KOC: Journey, Demon's Souls, Valkyria Chronicles, Uncharted 2 are the essential ones, I'd say (and SOTC / Ico Collection if you don't have them on PS2).
Personally I think the Killzone, Resistance, God of War and Infamous franchises are way overrated. They're pretty good, but hardly essential. There are much better multiplatform games (that are console-only) out there, such as Vanquish and Red Dead Redemption.
Yeah, exclusives aside it is actually Skyrim and Red Dead Redemption that are the first console games I'd buy. I'd like to pick up all the Bethesda RPGs and play them over time.
I'll go on Gamespot to read about the games suggested here so I can learn more about them. I tend to like RPGs the best but i like action games and shooters a lot as well. I do like Racing games too and would be happy if I found MX vs ATV in some form on PS3. I also like NFS games and Burnout, Flatout, etc. Something I love on the PS2 is SSX 3. I read about the Ratchet and Clank as well as Jak and Dexter series games (PS2 versions) and those sound like a lot of fun too. I probably should have mentioned preferences/interests like these to begin with.
Things I like about the PS3 over the Xbox for what it's worth:
1.) Includes Blueray player.
2.) No charge for online features
3.) Not sold by Microsoft. :-)
nagytow: I'd say: Uncharted, God of War, Infamous, Resistance
[url=http://en.wikipedia.org/wiki/Category:PlayStation_3-only_games]http://en.wikipedia.org/wiki/Category:PlayStation_3-only_games[/url]
[url=http://en.wikipedia.org/wiki/Category:Xbox_360-only_games]http://en.wikipedia.org/wiki/Category:Xbox_360-only_games[/url]
Thank you very much for those helpful links! I'll check those out.