Ok, to clarify my post:
Fox destroys puff, and is one of the most lopsided matchups in the game. Still, puff can win (as in, has a chance, as in the matchup is not 95-5). It's just that Fox has a huge advantage.
In melee, it's a similar idea I guess, but there are some one-sided matchups, like the marth vs pichu matchup, that marth just ***** pichu, and there is very little that Pichu can do about it.
Brawl, one-sided matchups are everywhere, most notably being the DDD infinitables, Sheik vs Ganon, and many more. Take Sheik vs Ganon for example. Both boards agree it to be 95-5 for Sheik. In other words, a Ganon should never beat a Sheik.
In 64, for the most part, any character can win. Usually first hit gets the stock (depending on how well they follow up the hit). Although Fox ***** puff, if puff gets one hit (huge if), then fox loses the stock. So even though Fox destroys puff, the puff can win, in that sense.
Basically, what I'm trying to say is that considering the most lopsided matchups in all 3 games, 64 is the most balanced, where it is more likely for the worse off character to win as compared to melee and brawl.