I am actively NOT interested in Green Lantern. I was reticent based on the casting alone (Ryan Reynolds is not Hal Jordan. Maybe Guy Gardner, but NOT Hal) , and then I was made even more so based on the promo shots of the costume. Seeing it in action in the trailer, I will most likely not bother seeing it at all. I love the universe and the characters too much to go and just be angered by the film.
XMen: FC, I have to see more before I can form an opinion. I don't feel the universe needed to be revistited again so soon after the last two movies were so bad, but I like Matthew Vaughn, and some of the leaked shots look interesting... so... wait and see.
Thor and Captain America both look interesting. I am going to give Thor the nod over Cap, though, since I have seen the trailer and think it looks VERY good. I need to see more of Chris Evans as Steve before I can get fully excited.
Long story short:
2) Captain America
3) X-Men: First Class
4 (Will Not See)) Green Lantern