Luckily I did already have a 360 that my friend bought me as a favor...
I was kind of craving certain number of 360 exclusives (Dead Rising, Condemned, Gears) prior to the gift, but what really pushed it over the edge was Bioshock.
I was playing Oblivion on the ps3 at the time, and all I kept hearing was this non-stop buzz for Bioshock. "What a stupid name for a game," I kept thinking. There's got to be a reason for the hype though...
Enter the wikipedia entry on Bioshock. I saw what the art was going to look like and fell instantly in love, stupid name and all.

To top it off, it seemed like there was no hope for a ps3 version that despite my distaste for Microsoft and business practices. So I had to cave in.
Like you said before, "1 year?" I think I could've waited, but it would've been a challenge.
Ironically, since COD4 came out, I've picked up both versions so I can play with anybody (that's my level of affection for the game), I haven't devoted any time to those old 360 games (yet). The 360's been silent for most part (all of my 360 friends who play COD4 defected over to ps3). I kind of want to play Mass Effect and/or Lost Odyssey but haven't picked them up due to time constraints.