The box office champ this summer will likely be Harry Potter. I suppose that Pirates could give it a run for its money with good word of mouth, but I think the last two films have left enough people jaded that it will not beat Potter. It'll make a **** load of money, mind you. But it won't be the champ. Potter is the movie to beat this year.
TF3 will do good. Probably 4th overall.
I predict a bad summer for Marvel. I think both Captain America and Thor will underperform. They won't do terribly, but I think they will probably do Incredible Hulk to Superman Returns numbers. The numbers won't be bad enough to be considered a bomb, but they won't be considered successful either. The studio will try to paint them as a success, all the while quietly nixing plans for sequels and just putting focus on The Avengers.
I think that Thor will out do Cap. At first I wasn't sure if they could sell a character like Thor to middle America, but I think it'll work on some level. I think good word of mouth will get it to 200 million domestic. It has the better release date with two competition free weeks, anyhow. Then again, maybe 200 million is all Marvel is counting on for a lesser known property about a Norse god. Maybe this summer won't be too bad for Marvel. Until July.
Cap on the other hand looks like any other movie Joe Johnston has ever made. Great atmospheres, looks cool in trailers, but that's because his movies are essentially two hour long trailers: action heavy and void of any heart or character (keep in mind, this is the guy who learned everything he knows from George Lucas). It'll open to mixed reviews and word of mouth and due to the fact that it is squeezed between Potter, Cowboys and Aliens (which could be a suprise hit), and the Smurfs (which may attract the kiddie audience) it will fizzle out around 150-170.
X-Men: First Class will pull in numbers slightly less than Wolverine as it does not have Hugh Jackman (or any major star) carryng it. 160-165 would be my prediction (domestically). Then again, it doesn't have much competition for two weeks so maybe it can break 200?
Green Lantern....I think its hard to predict. It looks corny and cliche with way too much CGI but that is the type of thing people eat up.
Hangover 2 will do well, but not Hangover well.
Cars could be a dark horse to beat Potter, but unlike most Pixar movies, I cannot see it attracting non-children. That'll hurt it.
Cowboys and Aliens is impossible to predict, with good word of mouth it could be huge....or it could flop entirely. Too hard to say at this point.
Super 8, I think will bomb and struggle to reach 100 million. Though it will develop a cult following in later years. The studio should've saved it for August.
My prediction for the top five:
1) Potter
2) Pirates
3) Cars
4) Transformers
5) Tough to say....either Kung Fu Panda 2, Thor, or GL.