If you noticed, Galaxy 2 scored higher than Galaxy 1 and the Megaman formula eventually got tired.Games aren't getting to the point where similar sequels are bad, for as long as I can remember it's always been that way. It's like that with films, books, music, everything.
More of the same isn't bad no, people love more of the same, to a point; things can get boring second time around if not much has changed.
And for me, I'm already bored of the new AC game and it's not even out.