Dungeons and Dragons settings:
Baldurs gate
Baldurs gate 2
Neverwinter Nights
Neverwinter nights 2 (expect to need a GOOD machine...)
Dungeons and Dragons Online - good game, but where the other titles are set in the forgotten realms. DDO is set in Ebberon, which is vastly different.
FFVII and VIII were released on the pc, but in order to make the most of them you should visit
http://qhiimm.com and look at a lot of the fan made patches (like the ones wich enable resolutions above 640*480, along with anti-aliasing etc... and some patches allow you to swap out the old midi tracks with mp3s. i swapped to the Black Mages recordings of most of the battle tracks and stuff, and threw in the AC version of "a one winged angel")
Knights of the old republic, is probably one of the best RPGs of the last 20 years, PERIOD. it's getting a little dated now, and i'm looking forward to a third installment (it's been announced, but there's no info..) the sequal wasn't as strong, it was very rushed, and there's a lot of cut content, but for the most part the series kicks major ass. it loosely uses the neverwinter nights engine and leveling system.
Gothic, as a series, completely owns. it's VERY open in terms of not having to have a set order to do things, you don't really have to side with anyone if you don't want to, and just generally tends to look great. the third game came out extremely strong in my opinion, and was better than Oblivion in the storyline department.
Elder scrolls was a good series too, but i always thought they pushed too hard on looks, and not enough on story and gameplay. check out the animations in oblivion, they make part of me die inside every time i play it...
too bored to write more, i'm off to own some sand people in KOTOR.