I was about to say Killzone. You got no choice really. There are very few FPS shooters on PS2. XBOX is a different story. Copp Killzone and wait for Area 51.
get call of duty,you will especially like it if you are a fan of the medal of honor series,dope game,just beat it last night...killzone is alright,but nothing special,i like the realism of call of duty,both solid FPS games but i prefer call of duty
I also recommend Call of Duty. Killzone was aight, I noticed a gang of glitches though-- the kind that really piss you off like getting stuck in a plant and you cant get out so you have to pull the pin from a gernade and off yourself just to start the level over. GAY.
those are some of the best ones for the ps2...an like snake said area 51 should be fuckin good too but it aint dropin til like april 2005 or somethin it got pushd back