Virtua Fighter 5

In Japan, where they take arcades seriously and no arcade game is taken as seriously as Virtua Fighter 5, regular updates rebalance the game based on player feedback and add new features. The latest update, Rev C, has made the usual miniscule combat tweaks as well as adding a handful of new costumes. Here's hoping they're standard on the 360 version and that Xbox Live is used to keep the game up to date, too.