Nintendo 64 and GameCube were more powerful than competition (though XBOX was strong than the GCN).
No. The N64 could load quicker, but it couldn't store as much memory as the PS1 or consistently have as much high quality graphics, although the DD would have fixed that. As for the GameCube, it was slightly stronger than the PS2, but it didn't have internet (aside from confusing accessories), and LAN was similarly complicated.
Also, the GameCube was terribly marketed, despite being possibly the best Nintendo home console since the SNES.
By comparison, Wii and Wii U are a generation behind the competition in terms of graphics.
The Wii was barely more powerful than the GameCube.
The Wii U blows the PS3 and Xbox 360 out of the water, and isn't too far behind the PS4 and Xbox One in terms of processing power. The problem is the Wii U uses a different type of memory and processing system (which is going to be the future likely of such things, and is a lot cheaper; the problem is, most 3rd party developers aren't as familiar with it as your typical RAM/CPU/GPU stuffers), as well as the fact the Wii U's online-related stuff is in a lot of ways 8 years behind (poor infrastructure, no voice chat, lack of online games, etc), as well as the fact that the Wii U doesn't have much storage memory.
Other than those issues, the Wii U is not too far behind the PS4 and Xbox One.
The problem is Nintendo couldn't find the right audience for ZombiU, NEW SMB U is a game we've played thrice before, Pikmin 3 has no multiplayer and probably not a lot of replay value, the Wonderful 101 is hard to market, and, oh yeah, until the last Super Mario 3D World trailer, nothing about that game looked interesting.
Fortunately on the Mario 3D World point they fixed it with that amazing trailer that showed the game for what it is: amazing.
Oh, and the marketing on Wii U Pad and online has been terrible. Nintendo isn't even marketing the fact that they're the only next gen console with high quality free online. Seriously, on Xbox One (and I think Xbox 360) you need to have Gold Membership ($5 a month) to use Netflix. WTF???