ok no real order here, i guess they all tie for first
Starcraft: I have spent so many hours playing this online. I love all the different scenerios and custom maps people have made. Great single player campaign too
Warcraft 3: The online play = awesome.
Final Fantasy 6, 9, and 4: My favourite 3. Probably go in that order too. Ive played through these 3 heaps of time.
Chrono Trigger: Beautiful story, music, characters EVERYTHING is beautiful!
Half-Life 2 (and the episodes): Excellant gameplay. It made you solve those cool puzzles to advance, and of course, GRAVITY GUN!
Treasure of the Rudras: I love how it plays out in 3 scenarios and you can use any spell you hear or see.
Star wars Battlefront 1 & 2: I ROCKED at these games.