I guess
Yes Man would be a HUGE hit during the summer, but now it's up against the great christmas-releases. It's still going to be huge, but a little less. (+ in most of Europe it's coming out early 2009)
I don't know what the second best hit will be ...
I wonder if
A Christmas Carol will have a huge audience. Okay, it's a big animation release, but to be honest ... how many times have they filmed this tired story already? I think they will have to do a realy great job on every level to convince the most of the people, not? Ofcourse there's the important names in the cast.
So I guess it will do just fine, but not huge.
As for
I Heart You, Philip Morris ... I don't know. In Europe by example the movie will be released one month after 'Yes Man', that will automaticly split a part of the people that want to see a comedy. Also, I doubt if this gay-issue is going to score realy, realy big. It will all depend on how strong and what kind the humor is and how good the trailers and stuff will sell it. If this film didn't have Jim Carrey, who is still a lot more succesfull then all those others new comedians overhere, I think it wouldn't be a solid hit. But we have Jim Carrey, so ... that could change everything.
My guess,
1. Yes Man (huge)
2. A Christmas Carol (fine)
3. I Love You, Philip Morris (Okay)