Probably MGS4 for me, but it's not even playable so I can't get too excited about it.
The only other thing I've seen that even slightly interests that is exclusive to the PS3 is Resistance: Fall Of Man. Looks to be pretty good, but with all the good looking FPS on 360, I'll be able to forget about it easily enough.
I really don't like how Untold Legends is looking for the PS3 and I can't get excited about Heavenly Sword when God of War 2 is still coming out for the PS2.
I don't know, it's really hard for me to get excited about these games with the PS3's price. It may be getting old to talk about it, but it definitely has an impact on my view on some of these games that I would be borderline interested in. At this point, I'm just hoping for a 360 port of MGS4.