Killzone 2, God Of War 3, GT5, Heavy Rain and Uncharted 2 are All Graphical Powerhouses and Exclusive to The Playstation 3.
Killzone 2 : From what we've seen from gameplay footage and beta impressions , it looks to be a Top tier FPS That can hang with the big dogs.

GOW3 : All God of War games thus far have been top notch. No "In Game" Footage has been shown only a 20 second teaser. But from David Jaffe's reaction about the game, surely PS3 God Of War fans are in for a real Treat.

GT5 : Gran Turismo is Gran Turismo, Polophony Digital are more than up to the Task of Making the Greatest Racing Sim period.

Heavy Rain : Quantic Dreams enters the next Generation with This new IP. Not much is known as of now, but the guys behind Farenheit (Indigo Prophecy to our Friends across the atlantic) Will hopefully pull of this ambitious feat.

Uncharted 2 : Uncharted 2 is the sequel to the first Must have PS3 Exclusive Uncharted. The Guys over at Naughty Dog were the first to showcase the power of the PS3 and part 2 will more than likely be even more impressive.
Here's hoping these 5 PS3 Exclusives can make it out on Time. 2009 looks to be a great year.

What do you guys think? What will be the best graphically? What will be the best overall. Could Heavy Rain be Genre defining? Only time will tell

Best graphically? I have no idea, I can't even say for sure which one of those it wouldn't be.
Best game over all? All but GT5 (or rather, I have no idea), not that it will be bad, but of all genres up there, racing is the one I get the least entertainment from.
I think Heavy Rain will in fact be something completely new, and a game that will go unmatched in terms of story telling for some time. Perhaps only until Quantic Dream makes their next game.

You said it best yourself, only time will tell

Apparently, God of War 3 looks ''fucking" amazing, you won't "fucking" believe it. With that said, I'm waiting for actual in-game footage of the game. ^^

Best game overall is probably going to be Uncharted 2. I loved the first one, and my gaming choices are always right.

And it is only doable with the power of teh C3LL.

one thing is for sure though, each game you have mentioned is on my purchase list, i am still a lil so so about heavy rain though it seems like the gameplay is going to be meh

I agree with all of them. Haven't seen much of heavy rain though.

I'll be buying buying KZ2, GT5, and U2 day 1 guaranteed

wasn't resistance 1 the first must have PS3 game? it sure sold like one as opposed to uncharted.

God of War 3 will fucking blow your fucking mind into fucking pieces................fuck...

Oh man! Here it goes again! @_@

5 graphical powerhouses that are out now-

1: Uncharted

2: MGS4

3: Heavenly Sword

4: Ratchet and Clank

5: Resistance 2

5 graphical powerhouses for 2009-

1: Killzone 2

2: God of War 3

3: Uncharted 2

4: Heavy Rain

5: Gran Turismo 5

I don't consider Heavy Rain as a powerhouse exclusive. There's not enough news on this game. Grand Turismo 5 will defnitely be a top seller just like the last three in the series and God of War III will be huge. The fact that someone from Nintendo likes Killzone 2, means a lot for this game and gives this game a lot of hope.