I envision Mario as a Fire Pokemon with base 100 stats across the board and has a sizeable movepool that reflects his versatility. He knows things like Flamethrower, Pyro Ball (sorry Cinderace), Rapid Spin (reference to his Galaxy stuff), Stomp, Taunt, Bounce (a stomping move too), Sky Uppercut (like his Up-B from Smash Bros.), Jump Kick, Rolling Kick (his dsmash from Smash Bros.); but he also knows weird moves like Minimize, Ice Ball, Wish Rollout, Fly, Hydro Pump, Wood Hammer, Power-up Punch, and so on.
Luigi is electric with a similar idea but is slower and has more health, and probably has more moves reflecting cowardice like Volt Switch, the Rattled Ability,
Bowser is probably Fire and Dragon with really high defensive and offensive stats but very low speed. Has moves like Flamethrower, Storm Throw, Earthquake, Heat Crash (sorry Emboar), Shell Trap (sorry Turtonator), Shell Smash, Withdraw, Spikes, Horn Attack, Rapid Spin, Outrage, Dragon Claw, Dragonbreath
Yoshi is probably speedy, but weak otherwise. Knows egg-related moves like Egg Bomb, Barrage, Softboiled, but also has things like Lick, Stomp, Power Whip, Earthquake, Flamethrower, and Fly. Has Gluttony ability.
Toad is reasonably fast and has a lot of power, but is frail. Knows Spore, Stun Spore, Poisonpowder, Giga Drain, etc but can also learn Barrage (throwing stuff), Rock Break, Baby Doll Eyes, I guess.