I'd get rid of the "generic" screenshots on the home page and replace it with the latest games like on the archive page and links to the most common categories.
Personally I'd like to see "best of week/month/year/all-time" and tags instead of categories (so I can find co-op + platformer)
Best of month/year might be even etter for the start page so new visitors see the good stuff (and maybe one game they already know is good, but not only games everyone knows already, so here you have to pick thte time range wisely or mix it manually)
Oh and embed some youtube video containing gameplay. Doesn't have to be a good one, just so you can quickly judge how the game feels.
One of my favorite browser games from several years back is Skrillex Quest: