This reminds me of a discussion I once had about similar subject...
There are two types of "fans" when it comes to, well, just about anything: true fans and "fleas".
Fleas are called such because they live off of various media as a source of nourishment, usually in the way of adopting portions of it into their own lives and personas. They take something from a media source and literally make it theirs.
A good example is die-hard Star Wars fans. These people would no sooner admit that the first three episodes were as bad as they were than admit that they have no purpose on this planet and summarily shuffle off into a large furnace. They CANNOT admit that something bearing the Star Wars logo is bad because to criticize it would be to criticize themselves. To these people, Star Wars is as important (if not more so) to their lives than religion is to most.
These are not real fans, because they do not see any error or room for improvement.
TRUE fans are the ones who respect a piece of media, be it a game, movie, book, etc., for what it is. They too will adopt pieces of it into their lives and enjoy their fanship thoroughly. There's nothing wrong with this, as I think we can all admit that it feels great to be passionate about something we enjoy.
However, what separates the fans from the fleas is that fans will see room for improvement where it exists. They will see when something that was once great is not living up to its former glory and they'll call it. As the series continues to drift away from its former greatness, the fans will also drift away, continuing to drift until they're no longer fans at all. They saw what was great in their favorite series and, as that greatness diminishes, so too does their love for it.
I once considered myself an avid Star Wars fan. I don't any longer. Episodes 1-3 thoroughly destroyed any love I once had for the series. It's both sad and ironic, but George Lucas wound up completely missing the point of why people loved Star Wars to begin with. It wasn't because of the special effects, it was because (though the acting was generally bad) the characters in episodes 4-6 absolutely OOZED humanity. This made the whole thing believable and enjoyable.
With the human element missing from 1-3 with stiff, lifeless characters, my reasons for liking the series ceased to exist (as it did for the majority of the series' fans). Yet, that hasn't stopped millions of fleas from marching right along, pretending as if everything as fine, as admitting otherwise would equate relinquishing a large part of who they are. Were Star Wars to die completely, the fleas would simply hop off the carcass onto the next warm host to suck nourishment from and start incorporating huge portions of it into their lives.
In summary, fans will see greatness and appreciate it for what it is, noticing when it diminishes and offering criticism upon how it could be better. Fleas will see greatness and latch onto it (mostly due to extreme insecurity), never admitting that there can be any fault found with it because doing so would equate admitting they were wrong about associating it into their lives to start with.