What are you talking about? The voice acting is one of the best part of Star Fox 64. Yes Slippy is annoying but you get gems from Peppy like the very popular "Do a Barrel Roll" or "Use the boost to get through" or Star Wolf's "Can't let you do that Star Fox"
Yes, absolutely. The amount of voice acting in Star Fox 64 was huge. It accounted for half of the game's 96 megs capacity, that's how huge it was. In other words, the voice acting alone was almost as big as the entirity of Super Mario 64.