Generations are a horrible way of thinking about consoles.
Or to be more correct, it ment something back in the SNES to PS2 days, and up through generation 6 there usually wasn't a big power difference between the most powerful and least powerful consoles within one generation, at least not compared to the vast oceans between the PS3/ 360 and the Wii or the PS4/ XB1 and the Wii U.
It's not like specs are irrelevant, but that somewhere between generations 6 and 8 it took a back seat to art style. Nintendo probably got off the power bandwagon a little too early, but Sony and Microsoft are definitely going to get off it too late. The human eye has a limit to how much detail it can absorb, and while the PS3/360 didn't get there, a few games got within spitting distance.
The Wii has a fair argument that it was the first Gen 8 console, because it was the first move away from focusing on power. The Wii U doesn't strike me as a Gen 8 console, either. Simply saying it's "between" generations 7 and 8 is a half-truth: it's just as much outside the generation system.
