Your Xbox (original) console and games are just as fun as they were one week ago. The Xbox 360 launch brings a lot of cool new opportunity for games. Abso-frickin-lutely. BUT! That has no bearing on what you're playing today.
Is that crawl through the jungles of Ghost Recon any less cool? Is that explosive vehicular destruction of Burnout Revenge any less exhilarating? Is that satisfaction of completing another mission in Splinter Cell suddenly boring?
If you don't have an Xbox 360 in hand... don't sweat it. You've got a ton of excellent games to play. Go to it.
Personally, I'm going to let the hype cool a bit. I'm effectively out of town until December 14th, so I don't "need" a system before then. Do I want one before my days off around xmas? Yup. Does it bother me that I don't have one now? Not in the least. I still have a stack of twenty-plus games that I would thoroughly enjoy playing to completion. I'm actually a bit sad that with the arrival of the 360, that I'll end up favoring 360 games over wrapping up my Xbox [original] games.