The complaint for me is that they updated Captain Falcon, Falco, Fox, Ganondorf, Kirby, Link, Lucario, Luigi, Mario, Marth, Mewtwo, Ness, Pikachu, Pit, Roy, Samus, Sonic, and I believe Yoshi and Zelda in the entire franchise. Whether those were just sound improvements like what happened to Captain Falcon, Marth, and Kirby, redos like Ness and Roy, or updating voices to match the current portrayals like Fox, Falco, Link, Luigi, Gaondorf, and Pit.
Since their debut, DK, Diddy, and Bowser never had updates to their voices. That's just bad. I mean, would you like it if Nintendo reused Mario's voice from Super Mario 64 in every game? That's just poor sound quality from age old technology. At the same time, none of those 3 are supposed to be realistic; they're supposed to be goofy. They evolved to be goofy characters with cartoon-y voices instead of realistic ones. I never played the DKC games, but at the very least, they could have updated DK to sound like a gorilla. At least Diddy sounds like a monkey. Bowser sounds threatening and funny with his official voice while his Smash voice just sounds stupid, cheap, and poorly done. It doesn't help that Smash 4 recycled voices which are okay for some like Link, Ike, and Mario, but recycling recycled assets really shows its age. And worse, some characters who were given updated voices sound bad. Mike West kind of sounded worse than in 64, 64 3D, and Zero where he was fine for Fox, Mark Lund sounds like his lines were phoned in which is fine for the apathetic Falco and isn't as grating as West's voice work in Smash 4, but it sounds lazy, and Palutena doesn't even have her Uprising actress, Ali Hillis. I appreciate and love the work voice actors do, so I don't like it when voice directions are shoddily done or done in a way that kind of doesn't portray a character well. It's why I like Jim Walker for Fox because you can hear his energy, how I like Roy's redone lines reflect Roy's older appearance, or how Antony del Rio really brings Pit to life instead of just reading off lines like Mark Lund for Falco. Nothing against any voice actors, but some voice directions aren't good. Telling Lund to be Falco isn't like telling Lund that Falco needs to be arrogant while saying, "You're off your game, Fox", or smug while saying, " Piece of cake."