TheCreator

That's hard to say as my tastes do change and that games are added as we go through more gaming generations. I would have to make a favorite game per system, which even then could I narrow down my choices a bit. I can't really choose the best ever, really, too many good things. I've made a list of things though which hopefully will allow me to stay on topic, nonetheless.
The game(series) I've spent the most time on is Pokemon(To avoid a lot of Pokemon it will be noted once here) .
Some games I enjoyed the story of but are not limited to:: Final Fantasy Tactics, Nier, Elder Scrolls IV: Oblivion, Fallout 3,Fallout: New Vegas(Lonesome Road, specifically) Persona 3, Catherine, Okage: Shadow King, Breath of Fire: Dragon Quarter, Chrono Trigger & Cross
Some of my favorite gameplay but not limited to:: Catherine, Persona 3, Shooter games usually, Fable(series), Disgaea(series)
Some of my favorite environments but not limited to:: Elder Scrolls(series), Borderlands, Silent Hill(series), Fable(series), Minecraft(technically), Breath of Fire: Dragon Quarter, Bioshock(series)
Some of my favorite Lore in games but not limited to:: Silent Hill(series), Fable(series), Final Fantasy(series, Most any of them), Breathe of Fire: Dragon Quarter
Some of my favorite multiplayer/coop but not limited to:: Jet Force Gemini, Super Smash Bros.(all), Vigilante 8, Mortal Kombat(series), Resident Evil(The Arcade Shooters), Shooters count for this, Borderlands(But terrible local interface though, bleh) GoldenEye

I could go on and on about this stuff, especially if I could remember all the games I've played. If you can tell these are some things in a game that make it hard for me to even decide for a Best game of any system