Mario has a lot of BS. Like straight up, he has very questionable attributes but everyone says "he's good but has little range".
No, that's not what it's all about. All of Mario's tools have very straightforward counter play.
Fireballs are an amazing projectile with their incredibly versatile angles. Loads of damage, very little cooldown means easy followup from SH fireballs.
Fireballs are good, sure, but they're very easy to avoid, and any aerial will go right through them. When Mario is camping with fireballs, I use back airs to hit through the fireball and continue to hit Mario. It's your job to make him feel unsafe using them. If he's getting follow ups out of them, that's probably your fault. Are you shielding the fireball when he is close enough to run in and grab? Instead, wavedash back and throw out a hitbox. Maybe wavedash or dash in under the fireball depending on your character's height. Or, if he's using it that close, just jump up and nair him.
Cape is cape. Look at the hitboxes on it. Sweetspot or just die. "But that's being edgeguarded!" Yeah but if I don't sweetspot and get Fsmashed by Marth I get a chance to tech, it won't kill me until 80%, and the edgeguard requires correct spacing.
Cape's hitboxes are pretty big, but I don't think that they're unreasonable. Especially since they're active for only three frames.
Counter play is contingent upon each character, but yeah, sweet spotting is usually the way to go.
Dash Attack is a long lasting hitbox and that's fine, but it needs like 5 more frames before IASA. For its great trajectory pop up you can follow up on it way too easily, especially since it can beat spot dodges.
Between the last active hitbox and Mario's FAF there are about 13 frames. Try shield grabbing or rolling past the attack instead of spot dodging.
His SJP is stupid. 7 frames of invincibility that cover half of the distance, leading into the craziest sweetspot grab box in the game, barring Luigi's Missile. Like, just increase the vertical distance and make the grab box actually part of the character and not a "easy free sweetspot for you" halo.
I'm not going to argue with this. I think that Mario has a very good recovery that is pretty difficult to exploit.
His smashes are crazy fast and powerful. I don't know if people realize this or are hiding behind "but range" but when a frame 3 (I'm pretty sure) Dsmash can kill a mid weight at 80%, with like lots of his smashes very little commitment, you've got a dangerous setup.
His forward smash is decently strong and fast, I'll give you that. But it doesn't make it completely safe to just throw out. Mixing in something like a pivot fsmash to catch a sloppy approach may be a nice mix up option, but it's certainly not spammable.
Mario's down smash is very weak and its speed matches its strength. It is active on frame 5 and has very low KB scaling. Check the doc in my signature and you can see how it matches up to other smash attacks in terms of raw power. It's certainly not killing any midweights at 80% unless they DI terribly.
I don't know why he's always like B tier on the lists posted here. H was considered top 10 in 3.02 like universally and his nerfs since then have been chump change compared to the overhauls Lucas and Diddy and Mewtwo got. I consider him a top 10 character.
People always quote him as a Jack of all trades, and while he may be master of none he's pretty darn good at most.
Edit: the final CT 3.02 tier list has him at fifth
Edit: forgot his down air. Move is crazy. Hitboxes have been decreased in size since 3.02 and multiplier normalized, but it's still so good.
Don't cite CT tier list as a reputable source.
The Mario match up becomes a lot more simple if you do two things:
1.) SDI and properly DI his combos.
2.) Respect his weight, ability to be comboed, and options out of CC.
First, SDI. This is huge in this match up. To put it in perspective, if I don't SDI any follow ups out of down throw at 0%, I'm hit for about 50%+. If I take the down throw and SDI the up smash which he usually follows up with, I can jump out and there are no follow ups. If you find yourself caught in a string of up air, you can DI down and away to avoid more follow ups. If he catches you with down air, I personally SDI up and out (the way he is facing), and I'll get out after a few hits.
Here are a few examples of how SDI helps:
Next, respecting his weight, ability to be comboed, and options out of CC.
Simply put, when you're comboing Samus, do you extend your combos as much as possible? No, she's too heavy/floaty. She's going to break out and nair you for trying. Mario is in a similar boat, albeit less extreme. You need to get your hits, get out, and reset the situation. Don't try and push a huge combo against him because it isn't going to work. Alternatively, instead of comboing for damage, combo for positioning. If you're Marth, put him above you where he has a difficult time coming down. As Ness, I like to put him off stage. You may not kill him directly, but you'll gain stage positioning.
He has good CC options like dtilt and down smash. Respect that, bait an option, and grab. It's all very simple.
I play this match up a lot. I think that Mario is a really solid character despite the counter play to him. But I don't think he's anything more than a low high tier/high mid tier.