i myself have a backlog of well over 400 games i need to play through. i'm hoping that i can strike it rich early, and then spend the rest of my life playing through every game that i own. its a nice hope, but probably not. a big chunk of the games i own, i own more for the sake of collecting, than to actually play. thats not to say that i dont play them all, but only around 200 or so are ones that i have or am planning on getting completely all the way through. number one on that list is to beat is the legend of zelda. i can't bring my self to do it, even though i have gotten to the final dungeon in the game for just about every version there is (nes, gameboy advance, gamecube.)
i usually wait until the system is older before i start buying most of the games. i've built my collection of older games mostly recently, off of ebay. i'm also now going through and buying all the good games for ps2, gamecube and xbox. the only system that i've been actively buying current games for consistently is the 360, but thats because i have a problem with needing achievements, as can be witnessed by the fact that i've only the 360 since june, and my gamerscore is over 20,000.