I know all there is to know about The original Zelda, Link To The Past, Mega Man 2, Mario Bros (the original, pre-Super),... honestly, too many to list.
But the one I'm currently learning everything about is Red Dead Redemption. I've already 100%'d the game, and I'm getting ready to prestige in 2 more levels in multiplayer.
Unlike modders and hackers, I'll be the first legitimate completionist, with over 5 solid days of gameplay so far... real time, since launch (broken up, of course. I'm not that obsessive.).