At the moment, most of the better games are FPS games!
Personal faves are FEAR, Resistance:Fall of man & Call of duty 3.
The Darkness is quite good, but is an acquired taste I think.
The Transformers is fun in a run around, smash things as a giant robot kinda way, and you also get to drive or fly depending on the Autobot/Decepticon you are playing.

I found Spidey 3 to be so-so, as it wasnt so different to Spidey 2 as they would have you believe!
Marvel Ultimate alliance is good as well, but once again, and acquired taste, plus it really does not make use of the PS3s power.

Motorstorm is a fun driving game, but I would avoid Ridge Racer 7 if I was you, unless of course, you were a fan of the way the previous games played (I have yet to try Need for speed carbon, so cant judge that).
F1 championship edition is great, but will probably only appeal to F1 fans!

Also worth picking up is Splinter Cell:double agent if you like stealthy games!

I havent really played any other games or demos as they either aint my thing, or I aint 100% sure I will like them.

Rainbow Six:Vegas is pretty good by all accounts, as is The Godfather:Dons edition from what my mate says! (we usually have similar taste in games)