The CPU, at the very least, is a custom design by IBM, so it's neither an off-the-shelf part, nor was it out in 2008.
The GPU in early dev kits was apparently from AMD's R700 series, which was released in 2008. It's unknown if there will be significant customisations to the chip for Nintendo, or even if the final GPU will in fact be a newer architecture, and the R700 was just used as a placeholder.
The RAM is almost certainly going to be of a variety that was available in 2008, unless they're using DDR4, which there is virtually zero chance of happening.
Anyway, even in the worst case scenario, the Wii U would be noticeably more powerful than the XBox360.