This is probably a bit hard to answer, especially for those who play a bunch of games and don't even remember what they've played a couple of years back.
I have four current favourites myself though:
1. Betrayal at Krondor: This game was simply fantastic when it entered the scene in the early '90's, much due to it's advanced graphics and an interface that was years ahead of it's time. The deciding factor for making this game my all time favourite though, is the incredible story.
2. Half-Life: Possibly the best FPS game ever made when matched up against the era in which it came. At the time, there was simply nothing in the genre that could even come close to the debth this game presented, and its safe to assume that the FPS genre as we know it would've been largely different without this game!
3. Final Fantasy VII: The defining console RPG in many peoples eyes, born in full 3D for the first time on the original Playstation. Visuals and effects were something we'd never seen before, and the depth of both the story and the gameplay blew any game, regardless of genre or platform, away at the time. It's legacy has been one of the most successfull gaming franchises of all time, and all installments of the series are multi-million sellers.
4. Gran Turismo: The king, grandfather and godfather of modern racing games. When it came out, we were playing stuff like need for speed 1 and 2, Top Gear Overdrive and Carmageddon. It was the racing genre's FFVII if you will; presenting debth and gameplay never before seen on any platform. The visuals and the sound was also leaps and bounds ahead of its contemporaries.
I do of course enjoy other games as well, but these are the finest I could muster from my own mind at least!
