I haven't seen this but ...
Captain Falcon drives a vehicle at nearly 500km/h. Unless it's the futuristic technology, his body must be pretty ****ing dense if he can withstand that speed without tearing into pieces. His reflexes must also be extraordinary given the nature of the F-Zero games and how precise turns must be. I think he needs a bit more slack. Plus, hello? Falcon Punch anyone?
Game and Watch isn't of a world. He's basically a God, but not an all knowing, all good or even all present one. He just is. Neutrality at it's finest. Realistically he has no named IQ, strength or weight. He's also thin, and as AA pointed out, this thinness would mean he is sharp. It could be argued he is infinitely thin. Would his mass be 0? Or is he indestructable.
Also, cases for Bowser are wonky. The entire Mario universe is really (except maybe Rosalina). The StarRod is possessed by Paper Bowser. If Paper Mario is in the next Smash, then this means Bowser and Paper Bowser are different entities. If this is the case, Bowser cannot summon the StarRod and wish invincibility. It's also questionable what Bowser we're speaking of as he always alters in size, ability, and strength. He's never truly been killed however - like ever. When does Bowser actually die? Could we argue he is just ridded from the world, like Gannondorf. And if this is the case, what about Mario and Luigi. Can they die? In their world, they have 1-ups. If we're having this discussion, there needs to be rules in the OP about what qualifies and what form of the character we're speaking of. Mario could hold a bunch of stars in his inventory. (Also, sidenote, if Bowser can summon the Star Rod, anyone from the universe can then so to speak. If the event was dire, they would wish on the starrod to defeat Mewtwo or Gannon. Although idk about Mewtwo, can Victini wish Mewtwo defeated? The loopsholes in this discussion are infinite)
Sonic is up there. I really am too tired to dig for numbers, but he is fast. I'd say he's the fastest out of anyone in this discussion. Mewtwo can warp, but Sonic can just meet up with him wherever he warps to. And Super Sonic .... well that's leagues above anything (if we give Sonic the emeralds, but even still, they would need to be in Sonics universe so he can maintain his form. Is it not true he needs 50 rings to go Super? Or will we go by SA2 where he just transforms?)
Also, are we talking personality traits? Sonic can be playful and end up screwing up the fight because of his cockiness. Pokemon trainer inevitably needs to summon and tell the Pokemon what to do - can an 11yr old be all that bright?
If items and wishes were taken into account then Ganondorf and Link would win every single fight. They both held the complete Triforce at some point and the Triforce is able to grant any wish you desire without the need to "summon it" or "use it", you just wish.
Let's create a sort of rule set for these matches and lets actually get the matches under way!
1-) Characters can only use items that are part of that character's identity - Single time items, or items that do not directly relate to that character are not usable
This means that characters like Link or Samus are able to use their whole arsenal of weapons, but things like the Star Rod or the complete Triforce which were only ever used once in a single game are not available for use. Items such as the Invincibility Star or the Chaos Emeralds can be used, but they would work exactly as they do on the games (meaning Mario would have to run after and catch an Invincibility Star and Sonic would have to "tranform" into Super Sonic, he wouldn't just instantly be Super).
2-) Characters do reflect their nature and/or personalities
Sonic is cocky, Kirby is innocent, Luigi is a wimp. All of these traits would actually be shown while fighting.
3-) Characters can use any ability that they themselves have used in any "cannon" portrayal (be it game, movie, anime or manga).
This means that Link would be able to use any item any of his past incarnations has used, the pokemons would be able to do anything that has been seen in the games, movies, anime and manga.
4-) The arena would be a vast open valley. There would be different terrains in the vicinity (in case a character could use a different terrain) such as mountains, rivers and a jungle.
This will help clear confusion as to where we are fighting.
5-) Before starting a fight both characters would be placed at the sides of the valley facing each other. A countdown is done down to 3 and then the fight would start.
6-) Fights are won only by killing or permanently incapacitating the opponent from fighting.
7-) There is no preparation before the countdown timer for the fight ends. Meaning no power-ups or gadget adjusting before a fight starts.
8-) No making up abilities unless it is something physically possible by the character.
What this means is that characters like Rosalina who have been known to create galaxies, stars and big bangs. She would be able to create things like supernovas or gigantic planets to smash them into opponents, but she wouldn't just be able to "kill her opponent because she has godlike powers". Try to remain as cannonly related as possible, if a character has not shown the ability to do something, unless its technically implied, he/she cannot do it.
9-) Characters do retain their physical stats. Olimar is less than one inch tall. Kirby is 6 inches tall, etc.
10-) Some rules from character universes are broken. The ridiculous ones that have no place in these fights.
Which ones do you ask? Well things like 1-Ups or Continues are present in most games and just do not have any place in this type of fights (unless the character is literally known for reviving). Things like: "He can kill any opponent in the game with this item so it should be able to kill all of the other fighters too" is also not taken into account unless the item/ability literally specifies that it is a one-hit kill to any living being.
Ok so with these rules let's present the fighters:
In order to shorten this discussion we will cut characters that are obviously inferior to other similar characters
Full Roster:
Mario (includes Dr. Mario)
Bowser
Peach
Luigi
Rosalina
Donkey Kong
Diddy Kong
Wario
Yoshi
Samus (incles ZSS)
Link (includes Toon Link)
Zelda (includes Sheik but not Hylia)
Ganondorf (includes Ganon)
Marth
Roy
Ike
Ness
Lucas
Pikachu
Pichu
Mewtwo
Lucario
Jigglypuff
Red (includes National Dex)
Pit
Palutena
Ice Climbers
Captain Falcon
Kirby
Meta Knight
King Dedede
Fox
Falco
Wolf
Olimar
R.O.B
Snake
Sonic
Megaman
Villager
Wii Fit Trainer
Plus these added popular choice fighters:
Ridley
King K. Rool
Dixie Kong
Little Mac
Takamaru
Chrom + Lucina
Pac Man
Mii
Now let's cut some obvious choices out and let's try to trim down each respective franchise to the "strongest" of each franchise as proven by cannon inside the franchise
Note: Franchises that don't have an obvious "strongest" will not be cut down
Full Roster:
Mario
Luigi
Bowser
Rosalina
Donkey Kong
Wario
Link
Zelda
Ganondorf
Samus
Pit
Palutena
Kirby
Meta Knight
Fox
Falco
Wolf
Captain Falcon
Mewtwo
Red
Marth
Ike
Ness
Mr. Game and Watch
Snake
Sonic
Megaman
Pac Man
Ridley
King K. Rool
Little Mac
Takamaru
Chrom + Lucina
Now let's further cut down those who are obviously outclassed (to the point where there is no debate possible) and have no way of actually being able to stand up a fight
Mario
Bowser
Rosalina
Link
Zelda
Ganondorf
Samus
Pit
Palutena
Kirby
Meta Knight
Fox
Falco
Wolf
Captain Falcon
Mewtwo
Red
Marth
Ike
Ness
Mr. Game and Watch
Sonic
Megaman
Pac Man
Ridley
And so this is our final roster. The way to declare the "strongest" is who can win the most fights. Obviously there are some fights a character will win and some a character will lose and as such some rock, paper, scissors scenarios will be brought up (I.E.: Ganondorf vs Link, Link vs Sonic, Sonic vs Ganondorf)
As such, the winning condition is who can beat the most characters out of this list.