If you like D&D the best thing to do is to go to the nearest Hobby Store and buy D&D Player's Hand Book 3.5e and play D&D with your friends at the table! You'll see that you can spend hours and nights playing the game without computer!
About computer games, I suggest Baldur's Gate 1 & 2. Planescape: Torment as Ubereil said, TES3: Morrowind as the best RPG ever built for PC... You can also wait for a year and buy TES4: Oblivion, but the game will be available only for those with monstrous machines (Pixel Shader 3.0, RAM as big as normal HDD <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />)...
