[PS2] I need some recommendations for ps2 action/adventure games

Beyond Good & Evil, definitely.

As far as the Castlevania games go, I loved Lament of Innocence, because even though the areas looked basically the same, there was that sense of Symphony of the Night exploration that I loved. It's a bit like playing a 3d platformer with a tinge of Devil May Cry.

The second one, Curse of Darkness, is all about the familiars that you get. Because you need to use them and have them fight in order to gain experience and level up, I found it got tedious pretty quick. Second strike against it is that as silly as the first one was, the second one was even sillier in terms of character design and plot.
I still plan on finishing it, and leveling up my familiars, but I've been putting it off because I have a lot of other, better games to play. If you really are starved for action games, or if you enjoy pokemon-type creature growth, it might be right up your alley.

Ratchet & Clank games are great if you like exploring and collecting stuff, and there's a lot to see and do, so it never really gets stale.

If you haven't played The Suffering, I highly recommend it. It's got a great mix of adventure style exploration (for ammo and story-related stuff) while keeping the action consistently high with the 3rd person shooter mechanics. Really I just loved seeing a game with the moxie to have a dark atmosphere, and keep it that way the whole way through.

Shadow of the Colossus is a great adventure/puzzle type game, but I'd be surprised if you hadn't heard of it by now. Definitely worth the $20, though.

Jam it back in, in the dark.