Modern Warefare 3? From what I've seen, it will not be worth buying. I've looked at the single player video, and it looked like most monotonous, repetative level I have ever seen. It looks the exact same as MW2 as well, if I showed someone a clip if MW2, then a clip of MW3, they would think it was the same game. The multiplayer dosn't sound too good at all, it sounds like they made it more unbalanced. After MW2, CoD has never failed to disappoint me.
I greatly enjoyed Battlefrild 3 Beta, but it sort of felt that DICE was trying to make it too much like CoD. But it was still great, the fluidity of the movement was a highlight for me, as well as the level of immersion. And that's in the multiplayer.
Either way, I keep feeling that FPSs nowadays are trying to be too much like CoD. I say bring something new to the table, other than more realism. I keep hoping for a new really solid Sci-fi shooter, but my wishes are still unfulfilled.