1. TES III: Morrowind (best game ever&forever, IMO)
2. TES IV: Oblivion (can't be compared with Morrowind)
3. Neverwinter Nights (i can't wait NWN2
)
4. Splinter Cell series.
There are also many other games i like, but i'm too lazy to type.
BTW, i would like to mention some less-known low-budget games written by various enthusiasts:
1.
Slay by Sean O'Connor (Very addictive strategy. Has won many awards) -> Shareware
2.
Last Rose in a desert garden, Infinite Ocean + some other games, all by Jonas Kyratzes (Excellent atmospheric adventure games. Highly recommended) -> Freeware