I also didn't care much for Halle as Storm, but oh well.
I think if and when they do the next sequal they should touch on her clostraphobia.
I wish they could have dealt with Rogue being Mystiques daughter and her relation with Miss Marvel, so she could fly and kick ass as well.
I would be very happy if they brought on Gambit, that would make my day, but I can't think of anyone who could do it. They'd probably have to get a newcomer like they did for Pyro (who was great)
Mr. Sinister would be a great addition too.
I don't think it would be good to have apocalypse though, they would need to have really good effects that don't look cheesy.

The part where Mystique and Magneto was taunting Rogue about her hair was soo cruel, childish but hilarious.

Overall I loved it, plus I was happy DeathStrike kicked Cyclops ass early because I never could stand his character.

Sometimes I think I'd be better off dead. No not me, you.