So, some of the current ports on the WiiU don't run quite as well as on the X360... WHO CARES? Does nobody here remember how terrible the first ports from the Dreamcast to the PS2 were? How about the god-awful ports from the SNES to the PS1? How about the port of HALO from the Xbox to the PC?? You needed like twice the power to run it at a halfway decent framrate on the PC vs. the Xbox. The so-called 'bad' WiiU ports are, for the most part, nowhere near as terrible as those examples. I've put a bit of time into BLOPS2 and have had maybe 2 brief framerate issues, aside from those it's very smooth. AC3 is silky smooth and looks incredible (I think it's the best looking console version). The rest have some issues, but are still absolutely playable, expecially considering these are first efforts!
Keep a few things in mind here...
1. Xbox 360 is going to have an advantage for these ports because it is the lead platform for most multiplats, so these games are optimized for the 360's architecture, not so much for other consoles. Think about this, X360 games are CPU intensive, using older shaders, on a very limited, early GPGPU. Since the Wii U's strong point is not the CPU, but its advanced GPGPU, CPU will be a bottleneck. Now flip it around, take a game designed to fully utilize the advanced GPGPU and newer shaders on the Wii U, coupled with the significantly higher GFLOPS available (most likely about double), and a game actually made specifically for the Wii U would have to be scaled back to work on the 360 or would choke that older, limited GPU! Architecture is a HUGE part of this.
2. The Wii U is BRAND NEW and runs on a different type of architectue than the last gen (a full featured GPGPU, brand new shaders, DX11 Equivalent features, etc.), this means that games will need to be coded differently to fully take advantage of this. The current games are ports, so are essentially emulating older technology.
3. When the PS4 and Nextbox come out, they will have similar architecture to the Wii U, meaning advanced DX11 type effects and shaders, the ability to offload physics and other processes to the GPGPU, etc. A game developed for the Nextbox will be running on architecture more similar to the Wii U, so should be easier to optimize for the Wii U even if it requires some minor scaling (think turning graphics settings from Highest on a top of the line PC to Middle or High on a mid-range PC).
4. PC Gaming is always considered to be far ahead of console gaming. The trend has been to use the GPU for more and more in-game processing, offloading that from the CPU to the GPGPU. This is why if you're building a budget gaming rig, it's always recommended to skimp on the processor/RAM a little vs. a high end system in order to get a better GPU. This is what Nintendo has done with the Wii U. It's smart from a cost and efficiency standpoint and will still get very good results when console games programmed for Next Gen architecture actually exist.
5. Specs are very preliminary, the 'Slow RAM' calculation is assuming single channel, I've yet to see somebody prove to me whether this is single or dual channel RAM, which could double the bandwidth. In any event, we don't yet know how much of a difference the faster EDRAM will make when it's actually put to good use.
6. Every speculation on power that I have seen shows the Wii U's GPU capabilities above the 360 and PS3 by a good margin in Fill Rate, Significantly higher in shader performance (around 4x I think), and at least double in GFLOPS. The current ports are simply not coded to take advantage of this.
7. In every gaming GEN, the first games released for a new console are generally at the low end graphically of what the console ends up producing a few years in. If the 'low end' of what the Wii U can do is equal to what the 360 and PS3 can do at the end of their life (AC3), that's not too shabby at all.
8. GOOD GOD, PEOPLE!!!
Here's my (realist) take on this. PS4/Nextbox will be more powerful that WiiU, but not by nearly as much as PS360 vs Wii. Modern, scalable game engines will result in games that look stellar on all systems, with some scaling of detail akin to PC games scaling between high-end and midrange systems. This will be negligable and the graphics will be pretty enough on all systems that few will really care. Scalable game engines and modern GPGPU's will actually make ports EASIER between the PS4/Nextbox/WiiU than between the current crop of consoles, resulting in less performance issues with ports. Nintendo's 1st party games will be absolutely, positively stunning. All the new consoles will be awesome in their own way, WiiU will get way more 3rd party support than Wii, Nintendo will own local multiplayer and killer 1st party titles, fanboys will continue to bash other consoles blindly... and I will enjoy gaming on my WiiU and Nextbox while appreciating the unique qualities of each.