Kind of confused, as I'm not sure what you're referring to when you say Baldur's Gate 2. It came out in 2000, not 2004, and currently runs at about $15 on Amazon for the collection of it and its expansion packs.
http://www.amazon.com/Baldurs-Gate-Collection-Shadows-Throne-Pc/dp/B00009ECGG/ref=sr_1_1?ie=UTF8&qid=1301353225&sr=8-1
I thought you might be referring to Neverwinter Nights 2, but that came out in 2006, and then I checked Icewind Dale 2, but that came out in 2002. Either way, NWN2 is the latest, and I can personally attest to the quality of its main storyline, as well as the first expansion. The second is kinda iffy, and I haven't played the third. You can get it for $20 on Amazon.
http://www.amazon.com/Neverwinter-Nights-2-Platinum-Pc/dp/B004GL1UH6/ref=sr_1_1?s=videogames&ie=UTF8&qid=1301353387&sr=1-1
As far as other options go, the market for cooperative RPG titles has kind of shrunken lately. Usually you're stuck choosing between single player games like Dragon Age and Fallout or MMO games that require monthly subscriptions like WoW or Eve. One game that comes to mind is Titan Quest, which is basically a really well done Diablo 2 rip-off set in Ancient Greece, Egypt, and China. Normally it runs for $20 but its 65% off on Amazon right now, a steal at $7.
http://www.amazon.com/Titan-Quest-Gold-Immortal-Throne-Pc/dp/B000WCCURW/ref=sr_1_1?s=videogames&ie=UTF8&qid=1301353783&sr=1-1
I'll rack my brain and see if I can think of anymore.
EDIT: Just realized that you meant Baldur's Gate 2 for the PS2. Durr. BG2 for the PC is a different game, and older, so the graphics are a bit dated. But the game itself is phenomenal.