It seems as though it's pretty difficult to get a precise handle on exactly how powerful the Wii U is compared to current gen systems. Comparisons between initial ports like Mass Effect 3 and Call of Duty: Black Ops II have not been favourable, but it's important to remember these are ports. Regardless of these comparisons, Reggie Fils-Aime has said, in an interview with CNN that third party games look "dramatically better" on Wii U.
When asked about the specs of the machine, and if they were comparable to current gen machines, Reggie replied...
The specs are quite different [compared to] the competitive systems, much more graphically intensive. If you do a side-by-side comparison you would actually see that third party games like Call of Duty look dramatically better on our system.
It wouldn't be stretching the imagination to state that future third party game might look better on the Wii U -- but considering Black Ops II struggles to maintain the same frame rate on the Wii U compared to the 360 and PS3 versions, the above statement seems a little disingenuous.
Still, it's a good interview -- and really good to see mainstream media outlets put together insightful interesting questions.