Guys like DK and Marth are no where near underrated. DK is beastly in this game and Marth....when has he not been a beast?
Most Underrated
Mario - Ironic that Nintendo's main mascot could be rated so low. Seriously, the tier listings have him lower than guys Bowser? Mario has barely any lag in his moveset, good combo ability, and edgeguarding tools that can own at least half the cast.
Link - Even though you have to work with him to win, he can be a very technical character. If he just had a real up+b after he uses a double jump, he'd be much higher. ****, where's the bomb jump when you need it?
Samus - Like Link, she has various techniques at her disposal, and holy **** at her recovery. And come to think of it, ZZS is on the underrated side too.
G-dorf - He's not as devastating compared to his Melee self, but he can still get the job done. Power, murder choke, and canceling some of the lag on moves helps him from suffering the same fate as Captain Falcon.
PT - Almost forgot about him. Out of the three, I'd say Charizard is the best, but I don't think Squirtle and Ivysaur are all that bad...well Squirtle at least.
Peach - She's been toned down a bit so that d-smash is pretty much crap, but she can still be a pain to fight.
Most Overrated
Falco - Why is he so high? Because of the spam blaster and chain grab of ***gotry? Without those, I doubt he'd be all that great. Plus his Up+B is as bad as Link's.
Snake - On the ground, he can be a real *******. But his aerials are ***.