Elite and Starglider on the ZX Spectrum were fantastic. But for me it is Half Life 2 on the PC. Played it again recently, and it's still unbelievable. Best game of all time, bar none!!!!
Oh man I spent soooo much time on that game. As for my favorite game, that's tough... I'd say Half Life is up there, and I love the Tempest arcade. Ask me on another day and I may give completely different answers. lol
Definitely Portal 2. No other game got me so thrilled throughout the whole experience.
After that, my other all-time favorites are Ocarina of Time, The Last of Us and Fallout 3.
"Big games" include CoD Black Ops, Dragon Age 1, Mass Effect series, Bayonetta and Deus Ex: Human Revolution. My favorite mobile games are Cut the Rope, Where's my Water?, Mini Dash and Rayman: Jungle Run.