"Nintendo Entertainment System" was the best brand name they ever had (Gameboy was also good), yet Nintendo threw it away for some reason. I guess its because they were so determined to shove 64 into the name somehow to illustrate that the N64 was a 64 bit system and therefore twice as powerful as the competition. They could have went with NES64 though. Then when the Gamecube rolled out it could have been called the NESCube or something.
That may have helped sales of those systems somewhat, because millions of people knew and loved the NES brand. Gamecube was a complete unknown.
As for Wii U, I agree 100% with Ian. The name is both stupid, and it also retains the Wii brand name which is my least favorite Nintendo system by far. Nintendo said they were going to make an effort to bring back the core gamers they lost, but with a name like Wii U they have already put the system on thin ice before it has even launched. I'm not saying it isn't impossible to win back core gamers, but with a name like Wii U it is now going to be an even more uphill battle than it was going to be anyway.
Nintendo somehow has to convince gamers that this new console is going to be badass and cool. Its like some kid with a funny name that's easy to make fun of moving to a new school and trying to make friends. Sure he can do it, but with his silly name its going to be much harder than it would be for a kid whose parents assigned a more dignified name.