Let's pretend that sequels (like B2W2) are completely out of the question, and that for the most part, very few totally new areas would be added and most improvements are to old areas - for this question, I'm considering only a game like Yellow, Crystal, Emerald or Platinum.
What is every single feature that you would want added/that would make you willing to call it a good game?
You can talk about specifically the things you wanted for USUM, or just speak generally.
What makes or breaks a third version for you?