PAX has been tight so far. The Duke Nukem forever booth was hilarious.
MVC3 is fun, as long as you forget all of your muscle memory from playing 2 because of the control change and the general floatiness and strange properties of the system (you cant cancel a dash with normals......unless you're crouching)
TERA seemed pretty neat, but all the demos I saw were all in the starting area and pretty vanilla looking, except for the combat which looks great.
Infamous 2 looks crazy in a good way, and their whole display booth setup was pretty elaborate and cool.
I didnt really catch most of the super big games, like halo and gears 3 (looks 100% more the same, at least from just watching the few minutes of a demo multiplayer match, not a bad thing I suppose), I also didnt feel like waiting in line for 2 hours to play dragon age II, because the first game was definitely not wait in line for hours good.