Pikachu v Meta Knight is 45-55; Meta Knight
Meta Knight, from a technical perspective, has far, far, far more than we do. Now, like many MUs that have slight disadvantages, we can still win, yes, it's just that it won't be because of the character but the player. Meta Knight has more than we do, much, much, much more, so it takes less work for Meta Knight to win given his wide range of tools; Pikachu has to really work for the win, given the insufficient amount of tools compared to Meta Knight.
Now, player wise, a Pikachu main vs a Meta Knight main would be 50-50 given most Meta Knight players won't be as skilled/dedicated as a Pikachu player; that is, they will not have as much knowledge on their character as we do for our character.