Quite sincerely they are all fine, and I say they are good representations.
is designed to be simple. His tilts and aerials have straightfoward functions, his smash attacks are fast and hit hard, and his mobility is easy to handle. His specials all educate on the simple special functions. Fireball is a projectile, Cape is a reflector, SJP is a recovery move, and FLUDD while unorthodox serve to teach about charge pressure and ledgeguarding. All of his specials represent Mario pretty well. FLUDD is "outdated," but there is nothing inherently wrong with it, and it is pretty good to Mario's gameplan.
is like Mario but more goofy and with more brute strength. In Smash is a mobile heavyweight with decent frame data who hits hard and is straightfoward. With his new grab animation, S4 dash attack, his facial animations, and his already iconic moves like Down B it is safe to assume he is well represented.
IMO was changed to BOTW as a fad.
was based on OoT but if you think about it his moveset was an amalgation of all the common Zelda stuff by that point (bombs, hookshot, boomerang, spin attack),
added the arrows.
followed the TP fad but he was fundamentally the same. I am also under the impression they changed Link as
would be coming back, thus the radical changes like normal grab and remote controlled bombs. His design was never unfaithful to Zelda games. He even got a less generic dash attack in Smash 4 to represent jump attack.
is well represented. No need for change.
has a moveset inspired by loose things in SF like deflecting projectiles, the rapid fire, the hand guns in SF SNES, and the general speed. His design in gameplay is functional, no need for change.
Some say she should be changed but much like Link, all of her common tools from Metroid are used in her design (Charge Shot, Missiles, Bomb, Screw Attack, Grapple Beam). Her made up moves have nothing inherently wrong with them either.
is well represented. No need for change.
has gained some of his own stuff over time but I think his Smash design represents him really well. Luigi has always been similar to Mario, but with his own flare of slippery attributes. S64 also gave origin to his goofy/coward persona.
represents MOTHER really well. It is a gimmicky game with a lot of silly attacks, which Ness does. A lot of his normal moves are product of Smash 64 low budget but they have gained uniqueness over the years adding in PSI effects.
has made up moves from the beta of Dragon King the Fighting Game. F-Zero racers have been parodies of common media characters, being an over-the-top meme factory represents that aspect well. F-Zero is also a game about speed and heavy punishment, which is what Captain Falcon does.
was a product of her popularity in 1998 and low budget, but her being a meme joke character is part of her design, which shouldn't be discarded for the sake of "faithful representation."