My two Nuka-Cola caps? Drop WoW and Diablo. WoW's an MMORPG, not a RPG, and Diablo is realtime Rogue with graphics, music, and sound.
Of the remaining 8:
1) Morrowind, with expansions. Sheer openendedness rawks.
2) Fallout, for setting the path towards all the RPG-goodliness, and being...