Well with God of War III released yesterday I think the PS3 library is pretty much untouchable at this point. It has the most variety and the best in each category. Especially RPG's since you said that's one of your favorite genres; Demon's Souls and Valkyria Chronicles are IMO the best RPG's released this gen and there's also White Knight Chronicles and Disgaea 3 (only talkin exclusives).
On the action side there's Heavenly Sword, inFAMOUS, Uncharted 1 & 2, and of course Metal Gear Solid 4. I'm playing God of War III right now and I honestly feel it's one of the best action games ever made. Even if you've been turned off by the ultra-violent style over substance, I really can't urge you to play it enough. Uncharted 2, God of War III, and Metal Gear Solid 4 are probably the 3 best games of this generation, let alone action/adventure games.
Since you already got an HDTV, the PS3 as a Blu Ray player sells it alone. But on top of that it's an TV-internet browser, DivX certified video codec player, and you can even help to cure cancer with it (not even joking).
You probably already have the games, but the Playstation Store has digital copies of PSOne games and is probably going to get PS2 games soon. There's a couple FF titles on there and Suikoden I believe as well. Dragon Quest VII is on the Japanese store, hopefully they bring it over soon but I wouldn't hold my breath.