When we talk about genres, there are a lot of things that are carried over to future installments. That's why we can categorize games: they have common elements from predecessors.
How much innovation do we need to classify a genre game that is far from rehash?
COD based on the future (we'll end up Halo-like or Resistance-like there)? A Zelda game with a non-humanoid character (we'll end up with Okami there)? WoW with technology (World of Starcraft)?
What's the innovation of Street Fighter IV, anyway?
Really, if we see something truly groundbreaking, then it'll probably be a new genre altogether. And then developers will make games on that genre. And then, it'll feel like rehash all over again.







