Hmm.... I guess for older consoles I base it off of the best fond memories and desire to play them again, and for the newer ones(that I can actually remember my experience with them) how much I actually played them.
- NES: Super Mario Bros 3
- Genesis: I sadly didn't have many games for this...
- Nintendo 64: Ocarina of Time
- GB/C: Either Pokemon Red/Blue or Link's Awakening
- PS1: Tomba!
- Dreamcast: Shenmue
- GBA: Minish Cap I suppose. The Metroid games were great too.
- PS2: Shadow of the Colossus. Lots of other candidates though... Kingdom Hearts, Okami, Metal Gear Solid 2.
- Gamecube: This is difficult... so many good games. Probably the most clocked in hours and just pure fun with friends/family was TimeSplitters Future Perfect though.
- DS: Castlevania: Dawn of Shadow
- Wii: Either of the Super Mario Galaxy games.
- PS3: Last of Us.
- Xbox 360: Uh... I dunno. Rock Band or Left 4 Dead 1/2. I mean I played my 360 more than my PS3, but it was mostly like CoD which I don't consider favorites/great, but can be fun online with friends(which is the only time I played them).
- 3DS: Zelda: Link Between Worlds.