This will obviously be opinionated, this entire thread.
Although:
I've played and mastered 4 characters while I played this game religiously, Peach, Luigi, Link, and Mewtwo.
I find that Link is the most overall balanced character. He is very strong, quick speed, nice grab via hookshot, good recover, a pure warrior, I've fought with 500% damage before being hit off. (with no tricks, straight up fighting and recovering when neccesary)
Luigi and Peach in second for different reasons:
Luigi's fireballs are nice to annoy people from afar, his charge attack is decent, his missile isn't too bad, his running attack is good to knock people off the edge, and his recover is the same as Mario's.
Peach has the best recover in the game. The golf club, tennis rachet, and Frying Pan are all powerful charge weapons, her hover is extremely useful, especially while fighting Giga Bowser, her parasol is a nice touch also, and the vegetables from Mario Bros 2 help also.
So this opinion is coming from someone who tried completely different types of characters in my history:
Link, a warrior, clearly
Luigi, the goofy, yet overall nicely-rounded character
Peach, the best recover, decent to cause damage
Mewtwo, the psychic with a very powerful charge shot, and dodging abilities
No you won't. I'm brilliant with Marth, i know i sound just like any other person on this thread and you will disregard my post and tell us who you are 'awesome' with and who you can 'beat us all' with but just think about, no matter what you write it will never be enough to prove you are better than myself, i'm invincible with Marth.
Spin.