Yeah, what he said.
I know I've said this elsewhere, but the battle in GOTU was exciting. The monsters were fast, the punches were hard, and they went every which-way. In G2 Gamera has a cool entrance, but then he just rams Legion and lets it push him backwards for the rest of the fight. It was like a really sad sumo fight. And the battle in G3 was awe-inspiring for the first minute, until Iris rams Gamera against a big wall. Then Gammy just stands there and gets molested by Iris. Not exciting.
I think they overmatched Gamera in G2 and G3, and instead of making the battle more fun, it just made them boring and...blah. It's a shame, as the rest of G3 is so great, the battle is a letdown...