Making judgements on systems that aren't even finalized is foolish. Of course, making judgements based on specs alone is even more so. It all comes down to the games.
Even Nintendo agrees with this...
Revolution Less PowerfulMyself, I'll be picking up an XBox360 since it is available soon, and there are games that I want to play on it (Perfect Dark Zero, Project Gotham Racing 3, Madden 06, etc.)
If/when the PS3 and Rev come out I'll probably pick up those as well, provided there are good games for them.
For the GCN, it appears that the focus has officially shifted to the Rev, leaving it to an early death. Rapidly declining sales, lack of games, premiere titles falling off the release list and/or being delayed, etc. I think everyone could see this happening for a long time. After all, if your best launch title is Luigi's Mansion, then you have a problem.