Dogmaus: I mostly play linear games, does Beyond Good & Evil counts as open world/exploration? There was a lot to explore, and it had PS2 and GameCube versions.
I haven't played BGE yet, although I've bought it on GOG, so i'm not sure - if you can travel between various places, without needing to do them in a certain order, like in the Elder Scrolls Games, or having interconnected areas you can choose to go like in Might and Magic 6-8 or like Baldur's Gate 1, those are a open world games, for example. :)
DreamedArtist: Only actual open world games I can think of is the GTA series and clones of that, driver, true crime stuff like that besides GTA.
Glaucos: Yakuza 1 and 2 are my favourite PS2 games, they both have a compact world to explore, but filled with many activities and side quests.
GUN was also fun with a small open world, but it's more linear than Yakuza and much more linear than any GTA.
DreamedArtist: Yakuza is a linier open world. One of my favorite game series ever. Hope one day GOG will get them here.
Did the first two games have anything censored out? I remember hearing that the later games had minigames and the host club deleted when it was brought over.