Here's my recomendation

RPG/Action RPG

Disgaea 3
Demon souls(AWSOME game!!)
Folklore

Action adventure

uncharted and soon uncharted 2
heavenly sword
MGS4
Ninja gaiden sigma
Infamous

Platformer

Ratchet and clank
LBP

Racing

MOTORSTORM pacific rift

I'm sorry, but if you have to mod a broken game to make it good, than the game is a failure.  I have a real hate for that game because every couple months I would start a different character thinking I will have fun playing as a mage/ranger/paladin/fighter etc. and just ended up wanting my time and dissapointed.

As for the other replies: I stand corrected, Uncharted is a TPS.  I think they are bundling the game with the PS3 now.

As for Prince of Persia: Doesn't easy and repetitve break the game?  The thing I remember liking best about the Sands of Time and Two Swords was the linear but well designed levels.  They were designed so well to prevent the feel of repetition.

PS3 Prince of persia is all about that: linear but very well designed levels. And it´s not as linear as the previous, there are many pathways just to get the 1001 lights. Prince has new moves and powers and can always return to every world and area to collect more lights. If you liked the 3 previous, you will love this last one. Only the first 15 mn are some kind of boring, then you get addicted to the game.

Try the best PS3 game so far Metal Gear Solid 4 I think most will agree!!!

If I could only give you one game recommendation it would be:

Uncharted (best characters in a video game this generation for me so far) You need to play the first before the sequel hits this Fall. I think Uncharted 2 will be one of my favorite games of all time!

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Action/Adventure runners up:
I would say MGS4 purely for the cinematic and amazingly high production values even if you haven't played the first 3.
Resident Evil 5, but only if you have a friend to play it with co-op.
Batman: Arkham Asylum - try the new demo on the playstation store, it convinced me to buy!

As for RPG's: I think Demon's Souls could fit your tastes when that releases in 2 months. As others have said you might like Folklore and Disgaea 3 for your RPG strategy fix. Watch for White Knight Chronicles and Borderlands in the future too. Borderlands combines RPG with FPS.

PSN: Get PixelJunk Monsters & PixelJunk Monsters Encore if you like tower defense games (2 players local co-op only).
Bionic Commando Rearmed was excellent as well.

UNCHARTED!

Get Super Mario galaxy. It's really fun and they just announced that its getting a sequel which will be even better.

What you cant get it on PS3 oh well ill leave....

Try out some demos in the PSN store. People can recommend you games but that doesn't mean you will like everyone. I know cause it happen to me plenty of times lol. Any way I recommend KZ2 and if you like baseball get MLB 09 The Show. Those are the 2 games I'm playing the most right now. Also MGS4 is a must get, which is the best game to come out this gen to me.

Uncharted
Ratchet & Clank: Tools of Destruction
Bioshock
Killzone 2
Prince of Persia
Resistance 1 & 2

There are many more but these are the ones that come to mind

And of course the fantastic inFamous!

Actually, I already own that game and have already finished it with getting all stars.  So....