If you recall a lot of people didn't think Wii would be competitive in the last gen. I count myself among those who didn't see how an SD console could be even as competitive as it's predecessor GC was. I still don't think Wii was a good console, but it still sold like hotcakes.
So to be honest I thought I could not predict well how Wii U would do, but the slow 3DS sales and rise of tablets made me think it wouldn't be another Wii.
In a way it may be bad that Wii U released first. Wii U still had competition from PS3/360 when it launched, and didn't compare well on price and game libraries.
By comparison when Wii released, PS2/Xbox were already pretty much out of mind for me. It was clear Wii games didn't look like the HD twins, but nobody was saying PS2/Xbox was better to own, and Nintendo successfully diverted attention from graphics, even making Mii characters look like preschooler art, as there was a new way to play.
