I purchased an Xbox 360 on launch day (yes, I was one of those nut jobs that camped outside a local Circuit city). The reason I chose the 360 was because MS wants this machine to be a media hub, not just a game machine. If the only deciding factor was graphics, it wouldnt not matter to me, but I love the idea of being able to access my movies, pictures and music from my computer downstairs.
I own all three current generation game systems, and I purchased the PS2 first because I had a play station one, and at the time a DVD player was still expensive. So not only could I still play my old games, I could play new games, and DVDs. Xbox really didnt have anything I really wanted. It did not have a previous console, and I had to buy a remote to play DVDs.
Then I bought my game cube cause i'm a RE freak, and I felt that game cube had better graphics than playstation 2.
Then I bought my Xbox because I wanted to play splinter cell, but with the best graphics.... that, and all the things you can do with a hacked Xbox.
PS3 is intreguing because of the blue-ray, and the multi-TV support. Granted, the demos as E3 looked great... but im waiting to see actual games run on actual hardware.
I know I love my 360, the ability of watching content on another storage device, especially my computer downstairs (about 600 gigs of movies), made it more than worth it. The backwards compatibility is only a small plus for me, considering I cannot get on XBL with my hacked box, but now I can play some of my XBL games on my 360.
I will probably be buying the next Nintendo machine, for the basic fact that I can download and play the entire old library on it, and play my game cube games (its busted right now). That and the last machine was cheap compared to the other 2. The next machine is rumored to cost $100.
I might buy a PS3, depending on capability and games. I like MGS, and thats about the only PS exclusive series Im interested in at the moment.
I dont think I will be catching the next 2 systems at launch. I dont have as much interest in them right now... but things might change, and I might be a nut job again, camping outside for the next piece of gaming fun.