Here's what I would do, though. Rather than committing to hosting games and downloads, which is quite a responsibility and expensive, as well, I would avoid these problems and the problems listed above entirely.
I would, instead, use Steam's API to create a website capable of a "max machine" search. You grab all the "recommended" GPU data for all the games, and do a little algorithm that allows people to pull up games that meet the requirement they input. You could also pull the top 6 game tags and let them choose those as well as search by title key words.
As opposed to having to work with publishers to distribute their earnings (and all the other stuff you have to worry about when you sell a game, like sales taxes, regional pricing, paying for downloads, etc.), you let Valve worry about all of that, and you support your site with advertising.