Wikipedia: Fan art or fanart is artwork that is based on a character, costume, item, or story that was created by someone other than the artist.
If you, as an "artist," create art that is based on any existing art, you are creating Fanart. It doesn't matter if you draw it in your own style or create your own characters. If it is not your original idea all together, you did not create it.
I understand the merit of developing ones own style; however, if your reason for drawing/painting/etc. is to honor a series or artist that you love, what is wrong with doing a reproduction? I find the increasing number of fan artists I see telling other fan artists that they need to develop their own style to be deeply offensive. By the definition of what you do, you are not creating anything; your argument has no ground to stand on.
(For the record, this has never happened to me. If it does, I fully intend to ignore it. When I want to make real art, I make real art; when I want to make fan art, I make fan art.)