Gfx most important? Hmm..
I wouldn't think gfx will compell people to buy games that much, and especially not the mass public. Apparently, this mass audience falls for games such as The Sims, instead of the new 64-bit textured triple-anti-aliased 50k polygon per nano-second pushing FPS. In any case, the video-game industry is getting more and more comparable to the movie-industry. Lots of complete BS appearing on the screen, but here and there you'll find a true gem or at least an enjoyable game/movie.
On the X-Box. My guess is that it will be the first console to introduce the wonderful downloadable patches. I am sure one of the main reasons to equip it with a standard net connection and a hard disk, is because developers will be able to go the PC way and release unfinished games. Other console builders (Sony, Sega, Nintendo) have a tradition of keeping to a very strikt Quality Assurance scheme, but MS.... The PC games they have published up till now haven't always been without bugs screaming for a patch. I'm sure they'll continue that way.
(Needless to say, I just hate the thought of MS entering the console market. It's the rich-kid-who-wants-it-all-to-seem-cool-but-simply-isn't-syndrome).