Game-Rate: Rating of online games
This site has a lot of information about online games - and these aren't just "web" games, either. Some use web pages, yes, but a few use Flash, and many use downloadable client software. Some games offer clients for both Windows and Mac OS X users, but many only offer Windows clients, since it is the most popular platform for gaming. The search options seem too limiting on game-rate.com; when I tell the site to show me games available for "Macintosh," I get no results, even though all the games listed as "Web-Based," "Win/Mac," or "Flash" should work just fine for Mac users.
While anonymous ratings are accepted, users who set up a free account will enjoy the benefit of their votes having "5 times more power" as compared to those of unregistered users.