The PS3 was also the cheapest blu ray player on the market when it released, let's not forget that. Yes, Multiplatform games looked better on 360, no denying that. That played a huge role in the 360's success. I bought every multiplat game on 360.
The Xbone won't have that advantage however, nor will it be capable of the best 1st party graphics. And it cost $100. That's just what it is.
Ryse looks very good, but I wouldn't go so far as to say it's the best game graphically at launch for either system. Killzone is a fantastic looking game, and it runs at 1080p, unlike Ryse. What really helps Ryse is it has better facial animation than Killzone.