Problem is, I think they always had to tone it down cause they wanted everything to be PG-13 (more ticket sales). For other things like Han saving the day or whatever, it was more of a surprise attack and he's suppose to be a pretty good pilot himself. Basically they needed him to do something useful so he wasn't just the guy that took people from point A to point B and went pew pew with his gun against Storm Troopers (whose guns shoot in crazy, fucked up angles lol).
While Anakin was in the Jedi Temple, he most likely would have come across some Knights and Masters as well. For some reason they didn't think it was screen worthy though
. I's probably safe to say that the majority of his badassness was left off-screen.
I'll agree that they probably failed in the representation of Vader. There could have been more legitimate battles with "quality" opponents, but by the time movies 4, 5, and 6 were made, the Jedi were near extinct and people like Boba Fett were employed by the empire.
Anyway, that's just my take on it.