I agree, you can't just break it down to one game only. I started with an Atari 2600, had the usual games, but it wasn't as much fun as going outside, riding my bike, and interacting with other 'kinders.'
I didn't really get into gaming until I got a GameBoy (X-Mas, 91). So Tetris definitely got my attention.
Got a Nintendo SNS (Jan 94), and the Legend of Zelda: A Link to the Past was EPIC. (It was also the only fantasy game I'd play; just not into wizards, goblins, fairies, etc.)
Fav' PC Game: Rome: Total War. You start off with two villages (if Roman, you're in Italy), and you have to build your towns, armies, allow trade, develop an economy, assist allies, etc. Eventually, the goal is to take +50 territories and Rome itself. To watch 10,000 virtual troops, cavalry, ballistas, etc. trying to kill each other while maintiaing formations is nothing short of awesome.
Console (PS3): the Assassin's Creed series. The first one was very redundant, with climbing over 50 towers to reveal the same tasks; you can pick up hundreds of faction flags and kill Templar knights...with nothing to show for it, not even a PS3 trophy! However, AS2, AS:Bro, and AS:Rev are so closely tied, it almost feels like one GIANT game, since I NEVER break between them. Towers can still be redundant, but the historical graphics, story and side missions, and the 'open world' (non-linear) gameplay are worth it. When done with one, I quickly switch and fire up the next in the time it take me to grab another beverage or use the can. lol Currently playing AS3 for the 3rd time now. I pre-ordered the Special Edition, got the Connor statue and Colonial flag.