my PS2 lasted forever :| and I bought 360 pretty late... still will get a few years out of it before it is obsolete.
but yea, I'm not really comfy with getting a PS3 either now since next year there will be an upgrade for a few hundred more and will last for a long time, still cheaper than a pc.
I still have the PC I had in 2002 and it still works fine. I have a more modern PC but I had no reason to get rid of my old one. It plays a variety of games dated beyond 2002. Thinking a PC goes out of date just because there's newer games out is what the PC companies want people to think. Chances are a middle-end PC bought in 2012 will be able to play any game released in the next five years. And if not, you can upgrade as you go along. I slowly added more RAM to my current PC as my needs rose and I've spent a total of maybe £30 on that.
Hell, I still have a working NES. They only go out of date when you have no reason to use them anymore. :)