Plutonas

first of all, the PPE, as a processing unit in itself is pretty simple. In fact, it can only handle two instructions at the time, and it processes them strictly in order. The end result is a CPU that is technologically less advanced than Athlon64. Luckily, the PPE is not supposed to do (much) on its own: It has the SPEs to fall back on. Each SPE is a fully independent microprocessor... but even more simplified than the PPE. The other problem is that neither the PPE or the SPE has a branch predictor, which means that a lot of the functionality that would have been expectedly incorporated in the chip design, has to be provided by software. This, amongst many other reasons, is why Cell has a significantly different theoretical and actual GFLOPS calculation. Keep this in mind when looking at the following numbers, which show theoretical and actual numbers for various CPU designs.

CHIP NAME | CLOCK SPEED -> THEORETICAL -> [ACTUAL]

Intel Core i7 980 XE | 3.33 GHz -> 107.55 GFLOPS -> [99 GFLOPS]
Intel Core i7 920 | 3.4 GHz -> 80+ GFLOPS -> [69 GFLOPS]
Broadway (Wii) | 729 MHz -> 2.4 GFLOPS
Cell (PS3) | 3.2 GHz -> 230.4 GFLOPS* -> [20.8 GFLOPS]
Xenon (360) | 3.2 GHz -> 96 GFLOPS -> [well below 57.6 GFLOPS**]
Power 7 (Wii U) | 3 GHz -> 99.36 GFLOPS -> [between 95-98 GFLOP]

* : The Cell has an extremely inflated 'theoretical' peak performance, which is impossible to be achieved due to the restrictions on PPE (and the way it is issuing orders to each SPE), bandwidth, as well as the limitation of only executing 'in order' instructions. Hence the huge differences.

** : The Xenon essentially is the Cell PPEs minus the SPEs. It has many of the Cell limitations, but it alleviates them considerably by being a more 'traditional' multi-core architecture. Still, it's 'practical' GFLOPS number is contested. It is definately however not above the 57 GFLOPS ballpark, and more likely in the 30-40.

*** : The Power7 is a huge improvement in terms of chip design over both Xenon and Cell. In fact, it is a superior chip design even when compared to the current state of the art Intel Core i7 series, which it manages to 'beat' on the same clocks. Additionally, due to its capability to run asynchronous, out-of-order instructions, it manages to eradicate many of the problems Cell fell into, and therefore it comes very close to maximising its theoretical GFLOPS figure. Do note that Power7 was designed to be able to do many things at once without problem, and this explains its superior performance.

tl;dr version: Just the CPU inside the Wii U, running at the most basic (minimum) speed of 3 GHz per core, will still be able to outperform PS3 by a factor of at least 4:1.