Why did the Arab spring back a few years ago fail for the most part, the Iranian green movement didn't get the result it wanted, but the European revolutions (such as French revolution in part or revolutions of 1848) were able to reform a continent with conservative religious views and a set of dictatorship governments into a significantly more free and liberal region?
History and Politics rarely accommodate with clear binary outcome. So, as much I would not say that the Arab Spring revolutions weren't a failure as a whole, I would also not say that the European ones were fully a success.
The European/American revolutions were not fully successful...
A revolution usually stem from a group of people unhappy about the current regime. They need to be strong enough to take out the regime, but to make it successful, they need to be clear what the desired outcome is. In that sense the American Revolution was successful in building a new independent country. But they failed to extend it to Canada. And whether it was the original intended purpose is also doubtful.
The French Revolution of 1789 was meant to imitate the English one from a century before. The purpose of many factions was to bring down absolutism, not all were in favour of a Republic. In any case, after the first struggle, the new governments had several phases like the Terror, where it was easy to lose one's head. Arguably, the French revolution could be considered achieved when Napoleon took the power with a Coup d'Etat, after about 10 years. Was it really a success?
In the comments, Bobson mentioned the Revolutions of 1848 as a resemblance to the 2011 revolutions in some Arab countries. But the Wikipedia page summarised it quite well,
It remains the most widespread revolutionary wave in European history, but reactionary forces regained control in each case, and the revolutions collapsed typically within a year.
So, were they really successful?
What the previously mentioned revolutions did succeed in, was to set some examples, some ideas, propose some alternative, which, in some case lead to some changes years later. Without the French Revolutions of 1789 and 1848, France probably wouldn't have been a Republic. Which it really achieved in 1871. And even at that time, there were discussions of bringing a King back.
... and the 2011 Revolutions weren't complete failure neither.
In 2016 you want to judge fully the outcome of those protests, revolutions, wars. It is probably too early.
Furthermore, if the revolution idea spread like a wave (partly due to Social Networks), the reality of each country is different. The causes and means were also quite different. To give a few examples
In Tunisia, the regime was changed, and (free) elections took place. Even if the country still struggles with terrorism and the place of Islam in their society, a change did occur relatively pacifically.
In Morocco, the King authorised a new Constitution, reducing (in name, at least) his powers.
In Egypt, the previous ruler was overthrown and some elections took place. But at the end, the "revolution" essentially strengthened the military control of the country.
In Libya, the government was removed with a strong support from Western powers. But the result is a completely failed country government.
In Iran, the regime stayed in place, but it possibly helped a more moderate side to win the election in 2013, leading to warmer discussions with the western powers, the end of the embargo, etc.
Depending on the metric you want to go by, those may or may not qualify as success. Many did bring political changes and often removed the dictatorship government that was in place.
Revolutions tend to fail rather often. Depending on your idea of what a success is, you could even say that no revolution ever achieved its goals in full - it's kind of hard when most revolutions were spearheaded by multiple groups with conflicting interests in the first place, and this applies to Arab Spring as easily as it does to the French Revolution.
"Revolution" doesn't mean "fight for freedom". Most revolutions were anything but, either in spirit or in execution. It simply means a fight to change the government / leading powers etc. - sometimes that means changing them for a democracy, both most of the time it's simply replacing one dictator for another (or one "democracy" for another "democracy" :P).
If you only include revolutions that declared a fight for freedom, you still have plenty that have a different idea of what freedom is e.g. freedom to do whatever doesn't conflict with others, freedom to comfortable life while someone else pays for your expenses or even freedom to live under a Christian dictatorship.
Even if you agree on what freedom means, the revolution rarely results in even that - the most common tendency is simply to replace the head(s) of the government, without any real change. French revolution was a great example of a reign of terror caused by the rebels "winning". The Hussite wars were about religious freedom, but they resulted in plenty of theocratic regions and caused a lot of damage to innocents. The American Revolution worked out well enough, but they never really had the full fledged bureaucratic structure to overthrow - they just wanted to get rid of their de iure overlords (and the taxes, tariffs and laws they didn't feel were fair, especially given their lack of representation), and there were still plenty of voices calling for a similar government, because this new-fangled freedom thing sounded new and dangerous. And as Monty Harder noted in the other answer, it was really a war of seccession rather than a revolution - there was never a goal of overthrowing the British government, just separating from it. The same is true of many "revolutions", including some that can be considered part of the Arab Spring - for example, the Kurd seccession efforts.
In the end, history is written by the victors. The Russian Bolshevik revolution was hailed as a succesful revolution, and was like that in the history books, but you'd be hard pressed to find any "common people" who profited from it - only the people in charge really changed, and most things just got worse. Sure, they got rid of the Czar, so the revolution succeeded - but it wasn't really a change for the better, so would you call that revolution successful? If so, plenty of the Arab Spring revolutions were "successful" as well, and some are still in progress. It's not like the French Revolution was just people raising and saying "Enough!" - they took up arms, and fought long and hard. Peaceful revolutions do exist, but they're quite rare - and usually build on a situation that's de facto already quite close to what the revolutionists are trying to enforce de iure.
Did they fail — and did Europeans succeed? First, I'm sure there are plenty who wished for a more conservative Islamic rule and to further distance themselves from the West during the Arab spring — and they got what they wanted!
When we look at the European revolutions... Lets take the French... The goal was "equality, liberty and fraternity", and to get rid of the chains of the Church, the Aristocracy and the King. In the long term, they succeeded in much of this; but one could claim that until very recent, they just swapped one chain from another. Rather than being beholden to their King and local lords, most became "serfs" of the local money-holders — those who could buy up land, own factories, offer jobs. Any rights for the working-class and any fair trade of money for work — and then money for products — is far from automatic. Nor did the revolution give people more food on the table.
If we look more immediately, The French Revolution ended with a reign of terror and an absence of justice, much worse than what the King had done. And within a few years, there sat an Emperor on the French throne — which would lead the country into war, calamity and starvation. And later, they got another King.
And while some — like those who had or could get money — made out well, other groups stood still or even back-slid because of the revolution. And some groups — especially women — had to wait very long for the promised "equality".
The end of the "Socialist revolution" ended with dictatorships. The end of the Communist bloc, ended with poverty and raging, uncontrolled capitalism and crime-syndicates — not much democracy. And if we look at Putin's Russia, they're on the way back to dictatorship — and possibly a new "Tsar".
The American Revolution — which started with declaring that people not only could rebel against an oppressive Government, but that they actually had a duty to do so — have ended with Government that wants to surveil its citizens 24/7 and to know all their secrets. It forces its will upon the world, and has coupled Christianity to itself in a way that's starting to become disturbing. And less said about the current election-cycle, the better...
So I'd say that the Arab Spring isn't worse — nor European Revolutions better — than revolutions in general.
"Did they fail — they succeed", answers above (which could be longer), show that your assumption is not correct. But I want to add some points:
If we see a revolution or a movement (Arab spring, 99%,...) stopped, it doesn't mean it is failed completely. The protesters are living in the country, some of them satisfied (by media, government arguments,...) some not; The more a government is sever, the more people will be unsatisfied. The revolution movement could resume any time.
The "Arab spring" suffered from lack of leadership.
Some reasons differs case by case:
In Egypt: the previous ruler was overthrew and Morsi elected as President. But he failed to act as people want. (He didn't improve economy. He continued to have good relationship with Saudi Arabia and Israel). Then he lost people's support.
In Bahrain: United States Navy base in Bahrain + Saudi Arabia. Note that Population of Bahrain is 1300000, So a little foreign interfere can have big effect.
In Iran: One revolution succeed in 1979. But the case what you called "green revolution", it was not in fact a revolution. In capital Tehran "Mousavi" had more votes but in the whole country "ex-president Ahmadinejad" had more. Mousavi refused to accept election results and you saw protests in Tehran. In the other cities there was not serious problems; only some protests with low population. But media exaggerated it as a revolution in country (because Mousavi was pro-western and Ahmadinejad was anti-israel). I was in Northwest of Iran at the time. A friend ask me about those who (he read on the internet) killed. I said there is not even one Wounded; A surprise for him.
In Yemen: it resulted in civil wars because of "Saudi Arabia's interfere" and not being united.
In Syria: We have world war not civil war. One side is US, EU, Turkey, Saudi Arabia, ... . Other side is Russia, Iran, Hezbollah,... ; China politically help this side.
Your comparison is "apples and oranges". The differences between the French revolution and Arab spring are huge, not least because of the cultural differences between the two regions and times. Even the more recent Russian revolution is very almost a century ago; and occurred in a country which was basically pre-industrial, in which many of the peasants regarded the Tsar as a living God.
In order to produce a meaningful comparison you'd have to choose contemporary European revolutions. The best comparison would probably be with Ukraine's 2004 Orange Revolution, and Georgia's 2003 Rose Revolution. Perhaps comparing specifically with Egypt and Iran's recent and respective revolutions. In that case they actually seem more similar than different.
After Egypt's revolutionary period the military returned the state to business as usual, and Ukraine's first post-revolution election saw the the president, whose corruption caused the revolution in the first place, re-elected. This led to business as usual in Ukraine, later sparking the Euromaidan protests. Post-Maidan Ukraine is a mess (like Libya or Syria), and even though the whole point of both uprisings was to tackle corruption; it's still a severe problem.
The reason things stayed the same seems largely because the revolutions didn't change their nation's structural problems. In comparison revolutionary France and Russia saw a complete overhaul of national institutions; for instance, Napoleon required the civil service to allocate people based on merit. Prior to this the "ancien regime" appointed jobs by the nobility of one's family. Fast forwards to the present, and the new elections and presidents were more cosmetic than effective. The institutions of the state remained the same; which is to say that in Egypt the military still monopolised power, and in Ukraine the oligarchs still monopolised power.
Ukraine's political instability continued in large part because of the demographics of the country. Ukraine's oligarchs belong to the Russian-speaking minority in the east, and are supported by Russia. The majority however do not identify as Russian, and have little of the country's wealth or power. Until this is remedied their frustrations are likely to result in continuing political unrest.
Egypt and Iran do not have the same dynamic, as their respective ethnic majorities control their most powerful institutions. These institutions also enjoy significant popular support. Both institutions; the military of Egypt and government of Iran also have extensive internal security apparatus, Iran especially... organisations instrumental in countering any revolts.
Why did the Arab spring back a few years ago fail for the most part, the Iranian green movement didn't get the result it wanted, ...
It takes a long time to assess the outcome of a revolution. We are too close to the Arab spring to say whether it is or isn't a success or failure.
Sooner would even argue that we don't know if the European revolutions or the American revolution is a success.
But more importantly, people's are different, cultures are different so it is entirely possible that we take different route to (different kinds of) success. I am a firm believer that it is likely that democracy isn't for everyone.
Case in point: For 80 percent of human history, the Chinese absolutely dominated the rest of the world, without having any sense of democracy.