3 things i would like to see in order of difficulty for the site developers.
#1. Most difficult, a seperate rating system on just the multyplayer part of the games, n/a for games without.
#2. Under the browse all games, provide more selections for multiplayer than just Massively-Multiplayer. Add in 2-player games, 3-player games, etc... also if this is done include extra search options like i have in my example below see #3.
#3. Provide more detail on the multiplayer and not be so vague. Like this game has 2-player co-op online only (like saints row 2) or 2-player co-op offline/online (Lego starwars), picked up saints row 2 only to find out its only online co-op so that was a waste of money.