Phantasy Star Online: Episode I & II
I really love this game.
I never got very far on the DC version. Only to level 40 or so. On GC, I was really obsessed with it. I got up to level 170 or more. But then I corrupted and lost everything. I was entirely legit too. It was really sad. I kept playing a bit more, to keep in touch with my buddies, but could only get back up to level 30 before I lost interest again.