I just recently got a PS2 and have a only a couple of games, I am needing help compiling a list of must haves. Here are the ones I have already: Kingdom Hearts, GTA: SA, Slugfest: unloaded, and Tony Hawk Underground 2.

Drakan 2: The Ancients' Gates

The original Monster Hunter, if you can find it.

Not sure if you own a PS3.. If not, I'd recommend picking up ICO, Shadow of the Colossus, FF X and XII (though I liked XII), and Okami.

Oh, and KH2.

Also, Drakengard, and maybe Drakengard 2. There's a third one in the works.

(Can't stop updating) I hear Viewtiful Joe is quite good. And definitely Psychonauts.

And I've always wanted to try Odin Sphere.

Oh snap, no one's mentioned Jak & Daxter?!

I'll check it out if I can find it.

Persona 3/4, Shadows of the Colossus and San Andreas come to mind immediately.

^ updated my post

http://en.wikipedia.org/wiki/Spyro:_Enter_the_Dragonfly was such a fun game for me. Try looking for that game (likely online).

I suppose I should say whats already on my list: Freedom fighters, Call of duty: finest hour, Brother in arms: something or other, Metal arms: glitch in the system, medal of honor: European asault, Destroy all Humans! 1&2, all of the GTAs. I'll think of more later.

Destroy All Humans is a must, along with Mercenaries. Also, (if you can ever find this game) try War of the Monsters. I played that game for so many hours. A simple 3D fighting game, but fun as hell playing as giant monsters beating the crap out of each other. A lot fun with a friend.

Both the Lego Star Wars.

http://www.youtube.com/watch?v=te_No0dapPY

http://www.youtube.com/watch?v=nt3ZTD5yZWc

http://www.youtube.com/watch?v=P4bIeJZoeCI
http://www.youtube.com/watch?v=LHJbE_kfybs
http://www.youtube.com/watch?v=2FG9x3x9LgI
http://www.youtube.com/watch?v=6RdbZeOxL2o

http://www.youtube.com/watch?v=p3Q14SEumEc
Xenosaga II
Xenosaga III

I'd say Spider-Man 2. I had so much fun with that game. Also, the original Tony Hawk Underground was pretty good.

Probably wouldn't be too difficult to find the game online, but I wouldn't bother since the servers were shut down a few years ago. The game is entertaining for awhile offline, but its charm really came from its online play. Once they shut the servers down I never played the game again. A damn shame, too .

These two, make sure you get Both Lego Star Wars games, Spider-man 2, and Tony Hawk Underground. Also the Ratchet and Clank series, and the Jak and Daxter series.

Sly Cooper 1-3 (don't get put off by the first, the second two are a lot better)

I must second Jak and Daxter! I'm going to try and pick up my old PS2 and get it running again soon.

Star Wars Battlefront 2, Shadow of the colossus, Scarface, Final Fantasy 8 and 9 are the first games that come to mind for me. All awesome games.

God of War 1 and 2

Devil May Cry 1 and 3

Viewtiful Joe

Okami

Beyond Good and Evil

Metal Gear Solid 3

Burnout: Revenge

Hitman: Blood Money

Prince of Persia trilogy

Disgaea: Hour of Darkness

Steambot Chronicles

I second all of those options! Three obscure but very solid titles!

I would hardly call them obscure, I had all of them at one point, but when my PS2 broke I sold my entire collection for like 100$, this was in like 2010 or something, I had like 70 games or so.