Not according to some people. I first became aware of this phenomenon when Burton's Dark Shadows was released. All of a sudden, I and many others were accused of not being "true fans" because we were actually looking forward to the movie, or because we hadn't watched the show when it first aired, never minding the fact that we may not have been born yet. It got seriously ugly in places.
A true fan doesn't need to know chapter and verse of the thing he or she is a fan of. They just have to enjoy it. So what if you haven't read/watched/played everything. All that matters is that you're having fun.