There a few xbox one games that operate at 720p despite the ps4 being 1080p so the xbox one is not far off being that console although nowadays 900p is the norm for xbone.
Make the xbone a little weaker, slow those cpu's down to 1.4ghz instead of 1.7ghz and perhaps drop the gpu speed a bit and you basically have that console, something capable of matching the ps4 but only at 720p. That is still a huge increase in power over wii u.
That's if you are truly matching the ps4 with everything except resolution. If you start reducing texture resolution, cutting back on some detail etc you can make a game that looks pretty similar but needs less resources.
I personally don't think the wii u ever needed to be that powerful. Between the ps3/360 and ps4/xbone there is a huge middle ground that Nintendo could have occupied but instead they went for marginally more gpu performance over 360/ps3 but marginally less cpu power than 360/ps3.
Something around 600-700 gflops for the gpu and perhaps 30,000 mips for the cpu would have been good. Easily achieved in the standard wii u case if they had gone for a 28nm or 22nm fabrication process not 45nm.
However lets face it many games don't push hardware, if you are doing 2D games or cartoon graphics instead of realistic graphics you don't need advanced hardware. I have a ps4 now and some of the indy stuff you see could be achieved on a sega saturn with as much detail if its just a 2D scroller. I've not seen many games that look like the are pushing that 1.8 teraflops of graphics power. A lot of the games would be just as good on wii u, ps3 and 360. Occasionally you see a game like Super Stardust Ultra where you think the older ps3 version is much better. Don't get me wrong though the ps4 is absolutely brilliant but its only a handful of games that justify the technnology so far. Other games are just nicely enhanced.
