One of the best features is the rating system, allowing gamers to numerically assess the various games they've played. Once ratings start rolling in, you can build up a good idea of a game's relative value: a handful of ratings means little (and unfortunately, some of my games have very few ratings, but there's probably because few people have played them), but once you're over around 30 votes I think you can form a fairly clear idea about the majority decision.
I thought it was interesting to take a snapshot of my games as listed on BGG (a bit earlier in March, when I made the screen grabs) and share the ratings (the Average Rating is the one to look at), and relative popularity based on copies owned/games played.
I think it's fair to say that my most popular rules - in terms of ratings and copies owned - are Lion Rampant and Dragon Rampant. Dux Bellorum is second highest with regard to copies owned, but that's been out so much longer. A couple of old magazine articles have been added somewhere along the line, but I'm not sure either really warrant being counted as 'games' (well, Beowulf maybe).
Head over to Boardgamegeek to explore more. Click on the images below to see larger versions.