I remember a lot of really old games that I used to play back when I was just a little kid.
I remember playing Monster Masher I think it was called on MS DOS, and I also played Treasure Cove, although I never beat either game. I then recall first playing the original Diablo, which was a sick game at the time. After that I got into Warcraft and Starcraft, and then eventually Half Life.
Once Half Life was released, I didn't play many games that weren't based on the Half Life platform, although not much came out that appealed to me other than Diablo II and a few other games here and there.
And now I am hooked on the Source Engine, I can't wait for more mods to be released that utilize this Engine.