Morrowind - Absolutely the best SP 1st person RPG I have played yet. I like the gaming system, and the attention to detail devoted to this game in general is exceptional. IMO, nothing compares to it yet. The ease of adding mods to this game is very pleasing, to say the least. It's pretty user friendly.
If you are looking for the finest RPG series ever, look no further than Baldur's Gate. Enough cannot be said of this series.
Planescape: Torment ranks right there with BG, and is slightly more engrossing in a personal way. I stayed up very late at night trying to gain my memories back.
A good time-killer for you: MechCommander 2. I liked that one alot. Toasting Battlemechs is always fun.
Another good time killer: Jedi Knight 2: Outcast. The stormtroopers die in a nice theatrical manner. One time, I kept shooting one as he fell, and he did somersaults in the air. Also, there is something satisfying about frying your opponents with Force Lightning. The graphics are sweet on this one.
Have fun!