The most important post-revolution objectives are to impart our political experience onto progressive alliances and to undermine Islamist groups. Otherwise you get shit like in Egypt, where the secularists, Coptics, and moderate Muslims all work at cross purposes when they should be a coalition and make rookie mistakes like abandoning their seats during negotiations, causing the Muslim Brotherhood to acquire Ultimate Power.
The whole democracy building part is really hard to do and quite unpredictable. You can see that in the former soviet bloc countries. Some are basically on a level with western Europe now, but there are others like Hungary, which seemed most promising for a long time, and is now on the way back to the 1930s by the look of some developments there.
I'm sure Afghanistan will go back to chaos, as soon as all western troops are out. The Muslim Brotherhood are not the most radical of Egypts islamists, only the most established in society, so that could still take a turn for the better. In other countries, we have to wait and see. If you impose too much influence, people will hate the west, if you do nothing, islamists have the best chances, as they are the most organized.
In Syria it's quite difficult to say what could come after Assad, and I guess that is the main reason why nobody has intervened so far. Turkey might want to intervene at some point, but they have their own interests, as Assad is backing the PKK.