Planescape Torment's a definite "must-play". "Must-read", anyway.
Do not try to run NWN2; it's a 2006 release, IIRC, but it's not exactly optimised well. The KotORs should run OK; KotOR II is a 2005 release, and while they occasionally have engine hiccups, you should be able to run at least on mid-settings, IMO.
Arcanum: Of Steamworks and Magick Obscura is meant to be good, not played it, though. If you're looking for "lighter" strategy, you might try Age of Mythology, which is quite good fun.