It's not bad to be a fanboy.
Just like it's not bad to be a christian, a muslim, a jew, or an athiest.
What it's bad to be is an extreme fanboy.
Or an extremist of anything, really.
I'm a fanboy, I'll admit it. However, I don't let my fanboyishness blind me to the lack of entertainment value of specific video games, or the high quality of new additions to old franchises [Fallout 3, anyone?]. All a fanboy is, really, is a boy that is a fan of something >_>
Extreme fanboys take it to a whole 'nother level, with a zealot-like fervor that rivals the Crusaders when they went to make all the Persians dead. They will never be pleased by anything that isn't exactly, wholly, and faithfully tailored to the past, which is a horrible way to be in any sense. They're so absorbed in their belief that such and such is god-like in it's gaming quality that they don't have any more fun with new stuff...
So no, it's not bad to be a fanboy -- It's bad to be an extreme fanboy.