I think it is 50% about gameplay and 30% visuals and 20%rest(sound,story)for the standard core gamer.
you can't sell a game only because of visuals.that may have worked with Myst and few other games but usually you need an interessting gameplay.
most of the top30 all time bestselling games have mediocre graphics but all have intuitiv gameplay and the only game that had great graphics and great gameplay(at the time when they were released) was gran turismo.Maybe Halo-but that's it.
COD or GTA never looked really great-and the rest are nintendo games with low-very low(kawashima,wii sports) graphic standards but (some of them)with timeless gameplay.
But as soon as we leave the top 30(30-200) graphic is becoming more and more relevant.
is it all about gameplay?no!if only gameplay was important nintendo would have stopped making consoles since the n64.
Graphics are important(if they weren't there would be no Hdtv)but i'd rather call it visuals,as it is not always about raw graphic power but visual style(UC3 looks great,but limbo,escape plan,muramasa and kirby also)







