The majority of my cosplay posts are sci-fi, fantasy, comic book or Disney related for the simple reason that then I know what I'm talking about. There's also a lot of video game cosplay out there, but since I'm not much of a gamer these days, it's not something that jumps out at me in the same way.
There are exceptions though. Like this cosplay by ChrixDesign. Again I'm only marginally familiar with the source material, but the work that must have gone into recreating this design outside of a game is impressive.