Fan Girl (Female equivalent)
A Fan Boy is a person who is an avid and sometimes violent supporter of their favorite console/genre/game/etc.
Fan Boys are very narrow minded. They will often Engage in discussions and arguments without taking in to consideration any perspectives outside of their own.
Console Fan Boys are well known to only ever buy and/or play their preffered console.
There are also reverse Fan Boys that, for example, will play anything except X-Box, but they're not as common as the regular ones.