The problem isn't fighting game characters in comparison to each other. The problem is how they're interpreted in Smash compared to their home games. Their animations, movesets, poses, etc. are all trying to emulate the home games as close as they can and while there is a charm to that, I find it incredibly boring.Terry is very different of Ryu and Ken; having similar gimmicks means little, is like comparing Little Mac with Cloud or Joker because of a meter that feels when dealing damage.
Heihachi or Sol would also bring a lot for Smash and wouldn't be comparable to the existing fighting game characters in the game.
Contrast Hero and Byleth where almost everything about them is either brand new or reinterpretated into something different from how it was in the original game.