Since there's no way I'll ever be able to pick one favoritest-geegolly-I-love-this-game game, I'm just going to list games that have kept my soul firmly in their pocket like so much change and a stick of gum for long periods of time.
It probably all started KOEI's original Romance of the Three Kingdoms title for 8-Bit NES.? Back in 1990, my brother and I used to drive our parents freaking bananas at the dinner table, talking about Cao Cao, Sun Ce, Lu Bu, Xiahou Yuan/Dun, Ma Teng, and all these other two-thousand-years-dead Chinese warlords.? They probably thought their nine-year-old was possessed.
After that, I'd have to say Shining Force and Shining Force 2 for Sega Genesis.? Holy crap.
Dragon Force for the Sega Saturn -- that game will always remind me of Megadeth's "Cryptic Writings" and Bruce Dickinson's "Accident of Birth."? Twisted Metal 2 for PS1 was a *great* party game, as was Virtua Fighter 2 for Saturn.? We used to have tournaments all through the winter of 8th grade, with about 20 people in one basement, every Friday night.
Final Fantasy VII on PC, as meh as it is now in retrospect, made me stay inside a lot during the summer of '98.
Shame on me for saying so, but The Sims would make entire days pass by without me noticing, back in '00.
And the most recent additions would have to be Star Wars -- Knights of the Old Republic on PC.? I played that way too many times.? I'm still feeling the ticks and jitters from just having cancelled my World of Warcraft account last week.? That was two years of my life down the drain, but it also got me a trip to Vegas, which was fun.? Now I find myself happily enjoying Oblivion on the PC, and other games on the PS2 I got last Christmas... God of War, Shadow of the Colossus, Guitar Hero I and II, Star Wars Battlefront, etc.
All in all, much of my life has been wasted on gaming.? Join the club, eh?