The Wii U didn't come out the gate like the Wii for a number of reasons; first and foremost being it's name.
The Wii was HIGHLY successful with the casual market, and casual gamers were/are confused about exactly what the WiiU is. This is an industry that's highly reliant on Numbered installments (PlayStation 3, Call of Duty 4, etc) so most of the casual market pretty much considered the WiiU an add on. Not to mention the system was HORRIBLY marketed to the casual base that made it so popular to begin with. You couple that with a completely different control type then what the previous generation had, and no MUST HAVE titles out the gate, and well.. your system is going to have a bad time.
I love my WiiU even though there really isn't a killer app for it at this time. But then again, the 3DS didn't exactly have any must have titles coming out the gate and took awhile to pick up steam. I think by Holiday season of this year the WiiU will have gained decent traction, what with the HD Re- Release of Wind Waker, and other titles like Shin Megami Tensei x Fire Emblem coming out.
You really can't compare the n64 to the WiiU, its more of a comparison to the GameCube if anything.