Before there was Halo, there was Marathon. If you thought Halo had a mad following, just wait until you run into one of these Marathon nuts. They swear by Bungie's old shooter and with good reason. Marathon is a very solid game and a more sophisticated alternative to the id classic, DOOM. But be warned, though Marathon is fun, it may turn your stomach. Marathon's bonus XBLA feature is motion sickness. Those with a strong stomach (or a medicinal cure) will find a fun and fairly lengthy adventure.