My list (in no particular order):
Fallout1 - could have gone with FO2, but with temple of trials, Yakuza, DEs, P90s, overdose of EEs and talking plants/radscorpions (didn't mind talking deathclaws) it was just too incongruous to compete with it's prequel.
PS:T - storytelling, atmosphere, dialogue, clever subversions, imaginative locations.
TES III: Morrowind - excellent setting and exploration, cool art design, pretty flexible magic, allows for diverse gameplay styles if you don't abuse broken mechanics. Would be easily surpassed by Daggerfall, if the latter was more finished, more diverse, did something with it's huge gameplay area and didn't send you on dungeon crawls on slightest provocation.
Wizardry 8 - excellent adventuring party atmosphere, good gameplay, replayability through party builds, and some hard to describe overall charm.
The Witcher - A New Hope.
Close misses:
Anachronox - would certainly make it on the list, if it was an RPG