I do like some of the voices, Knuckles, Shadow, Sonic, and Rouge are all pretty good. It might be how its implemented into the game that makes it sound worse. Knuckles saying now there to chao's is the best line in the game.
At the first sonic/shadow boss fight the lines are layed on top each other at the end of the conversation.
Holy shit, I might need to look into this more
Dreamcast: https://www.youtube.com/watch?v=ZxK8mkkOcDQ
Gamecube: https://www.youtube.com/watch?v=WhGm4ztXeMs
Yep, it seems that they fucked up the audio for some parts of the gamecube one.