IMHO its way to early to write off the Wii U as being under powered vs the current gen, or even barely capable of suprassing them. No question that the system wont be anywhere near the next Playstation or Xbox, but i think a lot of the critisism and negativity in this thread is premature and unfair.
A lot of the 3rd party games that have been ported to the Wii U, ie Assasin's Creed 3, Mass Effect 3, COD 3 etc, are running on engines that were originally developed for the Xbox 360 and PS3. Also a lof of these games appear to have been ported to the Wii U by small teams, within short periods of time, and with limited budgets. Then we have the architectural differences between the Wii U and the HD twins, they appear to be quite significant. Despite all this complexities, the Wii U version of Mass Effect 3 runs at a higher average frame rate then the PS3.
Also from what has been said by GAF members like Matt, most if not all of the current 3rd party titles out at launch were developed on immature and older SDKs. Lets see how things improve once the SDKs mature, system updates, developer understanding of the architecture improves, middleware tools envolve, and we start seeing engines built specifically for the Wii U.
Once these things happen, that's when we'll be able to gauge realistically the capabilities of the Wii U.