I don't really have a backlog. I don't buy a game (or rent it) until I know I can play it...unless it's super rare.
Just seems like a lot of wasted cash.
I used to be like you. I think posting at GAF got me more interested in TEH RELEASE DATE, so I'd buy a game i knew I would like on day 1 even though I'd already done the same thing with another game 2 or 3 weeks earlier. So one or both would wind up half-finished.
The last 4-5 months or so though, I've finished every single game I've bought, except Mass Effect (which I really haven't started, I got it as a gift anyway).
To anyone who can't get a grip on their list of shit to do, try
www.backloggery.com. Beating games is like getting Achievements. I put all my current-gen shit up on there a month or so ago, I've beaten a number of backlog games in that time (as oppose to only beating new games last fall).