Uncharted is one the prettiest video game I've ever played. The environments, player models, textures, lighting, water effects etc are all top notch. And this is only the first one! I can't wait to see how good 2 and 3 look! It's also a blast to play as well!
If you have a PS3 and don't have any of the Uncharted games then that thing is going to waste. The gaming experience that those games provide is something else. I think Metal Gear Solid 4 has better graphics overall but I think they were aiming for realism and that's not always gonna give you the prettiest visuals. Meanwhile, the guys behind Uncharted focused on making a damn pretty game and I appreciate that.
And it doesn't get too bogged down in telling a super complex story, it just tells you what you need to know and lets you have fun. And it's very easy to pick up and play, not a lot of things put in there that'd stop you from actually playing the game.
I've played 1 and 2 and in both instances, I played them from start to finish. It's so damn fun (sorry for repeatedly using that word) and it's hard to put down.
I second the metal gear 2 and 3 love, and if you want to see how it all starts you can play part 1 on the ps2 as well, since that system is backwards compatible.
Definitely give Metal Gear Solid 1 a go if you can. As great as games have been since then, that's still my favourite gaming experience of all time. It's one of the games that started this whole cinematic trend in gaming. The Psycho Mantis battle game me CHILLS! All the boss battles were fantastic.
If you have a Game Cube by any chance, they did a remake of Metal Gear Solid (called Twin Snakes) and that has updated gameplay from MGS2 (like going into first person mode when shooting and some other things).
I'm a few years behind in gaming as well, some PS2 games I played over the 00s that you might dig are:
God of War 1 and 2
Okami
Shadow of the Colossus
Resident Evil 4
Those are some good suggestions. I'm not a big fan of the God of War games (not really sure why but I could never get into them) but they're good. I much preferred the Devil May Cry series. I never played 2 but 1 was very enjoyable and 3 is a major improvement.
Have a look at some gaming sites, I know a few of them have a "top PS2 games" section. That should give you an idea of what awesome games are available. Lots of great games to play, it should keep you busy for a while

As far as great PS2 games go, it doesn't get much better than Ratchet and Clank. One of my favorite video game franchises of all time.
YES! I played 3 from start to finish on the night before my wedding

Speaking of retro gaming, my girlfriend bought me a PSP for Christmas. Total surprise, but that was half the fun for me. It's a rare case when I don't already know 90% of what's available. It's been fun figuring out what's out there, what's likely to be worth playing, and what other stuff I can do with it. She gave me some credit at a local game store along with the system, so I got:
Metal Gear Solid: Peace Walker
Tactics Ogre
Jeanne D'Arc (strategy RPG)
Little Big Planet
I'm playing Tactics Ogre first and digging it.
I got a PSP when it first came out but I haven't used it all that much. I'm not a big fan of the physical device but the games on it are fantastic. I hope they eventually port the games to something that I'd feel like playing them on.
By the way, Metal Gear Solid fans that have a PS3 should keep an eye out for the Metal Gear Solid HD collection. They're remastering 2, 3 and Peace Walker in HD.