#1. Original Deus Ex. For its time it was simply amazing.
#2. Planescape Torment.
#3. Morrowind
Honorable mentions to Akalabeth, Wizardry, Ultima III, Diablo II, Starcraft, KOTOR and original Fallouts.
The most time I've sunk into any game was eve online (2006-2010). But I don't consider...