40. Mechwarrior 2: 31st Century Combat (Activision, 1995)
Stomping around kicking ass in a giant robot is what video games were built on, and Mechwarrior 2 remains a standout of the genre, even twenty-five years after its original release and numerous sequels. I can certainly see why, too - the game looked and played fantastically for 1995, combining elements of vehicle simulation, first person combat and even a surprisingly good storyline with two distinct campaigns. On top of all that, the game had two expansions (Ghost Bear's Legacy and the standalone Mercenaries) and even featured online play over "NetMech". A rockin' good time that took full advantage of everything PC hardware was capable of at the time, and a devoted fanbase releasing all sorts of tweaks and upgrades ensures that it remains an excellent experience even today.
39. Commander Keen in Goodbye Galaxy! (id Software, 1991)
38. Toonstruck (Burst Studios, 1996)
37. Carmageddon (Stainless Games, 1997)
36. Lemmings (DMA Design, 1991)
33. Tetris (Alexei Pajitnov, 1984+)
32. X-COM: UFO Defense (Mythos Games/Microprose Software, 1995)