I was going to recommend Anachronox, but then I read that you didn't want anything too Quake II-ish, and Anachronox is based on the Quake II engine, so...er... Still worth a look if you can overlook the graphics. It's far from perfect (and slaps you with a pretty horrible cliffhanger ending due to budget cuts), but it's silly, self-mocking, and pretty fun. It's also very, very J-RPG styled, and sci-fi themed.

The trouble with PC RPGs is that most of the classics are er...classic. It's not exactly a flourishing genre, and most of the best examples are six or seven years old at least. Ignoring your graphics requirement for a moment, though, I'd also recommend System Shock II with every fibre of my being. It's not exactly an RPG. More of an RPG-FPS hybrid. But it is absolutely beyond great. =o