I fail to see why anyone would constrain their thinking to believe it has to be one or the other.
It's always been an issue of balance even though visuals have typically been the impetus that drives consumer interest in projects in development, months, if not years prior to the actual release. (for the obvious reason that you can't have an opinion on game play until you actually play the finished product.)
It's not a reason to buy the final product if the game simply isn't fun or engaging though, which should go without saying.
Ultimately it's the game play that keeps people interested in a title, which typically has a positive effect on long term sales.
But the console industry is tech driven as much as it is design driven, and standards for what is considered to be acceptable change with each generation. Keeping up with current standards is a key contributing factor in keeping the industry dynamic.
Very few people would still be playing on 8-bit systems even if games continued to be churned out on them. History has shown that when developers near the ceiling of hardware constraints, the platform itself begins to become a liability in terms of design limitations as well.
If someone asks which do you believe is more important, visuals or game play, the answer should be "Both." They are not mutually exclusive by any standard.
