I guess I have to talk about Jiggs, since I'm uniquely qualified to do so.
I played only Jiggs in Melee, was considered for a few years to be the best Jiggs in Brawl (a half-joke title, since no one played Jiggs), and at least won one local tourney in Smash 4 with Jiggs.
I don't want to get into a data dump comparing all 3 Jiggs, but I'll try to cover the high level stuff.
In all three games, Jigglypuff is an aerial-focused character dependent almost exclusively on spacing, who has a f1-invincible wild-card kill move in the form of Rest. Her ground game revolves around high-damage throws and a formidable dash attack. She suffers intensely at being out-disjointed, and her handful-of-aerials-moveset is impacted more intensely by stale moves than any other character. Sing, d-tilt, and d-smash are not actually moves, just extra taunts.
Melee Jiggs is a pretty broken cheese character with abusive edgeguarding, insta-kill Rest combos, and hardcore planking potential. I think the other top characters are clearly better, but these 3 aspects are so borked that Jigglypuff will never not be viable (at all levels of play) in Melee.
Brawl Jiggs had Rest neutered to the point of uselessness in most matchups, though it was still useful against MK, Diddy, and as a hail mary against the likes of G&W. Bair WoP was ruined by the changes in knockback, the reduction in hitstun, and the new air dodge, but it was still workable against Snake. Fair became an all-purpose spacing and KO move. Rollout was no longer helpless off-stage, and was a shockingly okay move in advantage and off-stage recovery situations. DACUS, a great dash grab, and decent roll options gave her a workable defensive ground game. She also had a very situational but plausible jab-lock. Jiggs was unambiguously one of the worst characters in Brawl, but more viable than probably any of her bottom-tier peers due to shockingly decent matchups against MK, ICs, and Diddy, the latter of which she actually countered. In her worst matchups, Jigglypuff relied on Pound's priority as a crutch--able to win virtually any exchange with a hard read.
Smash 4 Jiggs, first off, is without a doubt overall better than Brawl Jiggs.
- She favors more hitstun.
- Bair hits like a truck, and has the insane 13% 100kbg hitbox that Sheik fair had in Melee.
- Fair is no longer doing double duty as her primary spacing tool and only aerial KO option.
- Nair is more useful than ever.
- More recoveries are back in the gimpable range, while her recovery is still solid.
- Rest is worth using again, even if it's not broken.
- Roster-wide nerfs to disjointedness, her true bane. (Her worst matchups were G&W, Marth, Snake, Olimar...)
- Shield nerfs make Pound super scary!
Obviously, as many have said, it's not all good though. In fact, there's tons of bad things:
- Her moveset is slower and less spamable, especially bair.
- No DACUS.
- No ledge-hogging, which favored her quite a bit.
- Significant reduction in Pound's travel distance, neutering it as a trump card.
- Significant reduction in rising Pound's vertical gain, hurting her recovery quite a bit.
- Rollout bounces off shields, making it truly useless as a recovery option in all matchups.
- Dash grab distance nerfed.
- Jab-lock removed.
- Safety of air-dodging into the ground, an option that meant more to her than others, was killed.
- Non-star-KOs off top are more common. (Affects Rest safety)
- Vertical KOs are more dominant in the meta. (And Jigglypuff's gravity is the least.)
- Rage. (Relatively helps heavies and hurts lightweights)
- Her customs are garbage.
Ultimately, Jigglypuff lost a lot of
options, but her
fundamentals were overall improved substantially from Brawl--and this is a case where fundamentals outweigh gimmicks. I can
promise you, from my pitiful position of a premier Brawl Jigglypuff player, that Jigglypuff is a better character with better overall matchup ratios in the Smash 4 environment, even if she's not particularly good and I frankly dislike playing her.
I think people underestimate the wild-card potential that Rest has. People will say "oh, but Ganon is always 3 reads away from a win, can we ever truly dismiss that?" I mean, I think Ganon is underrated, but uh...
yeah, we can. (Did you play Brawl?)
But Rest, as a f1 invincible move, that does great damage and KOs pretty early? Frankly,
no, I
don't think we can ever fully dismiss that. In Brawl we more or less could, but in Smash 4 I don't buy it; the KO potential is too real.
It wouldn't be hard at all to make Jiggs good or even broken in Smash 4. Turning the timing dials on bair would go a long way, as would reverting distances on Pound. I'd like to see fixes to Rollout myself--both no bouncing off shields, and the changes we did in BBrawl. (IASA on bounce, allow interrupt by pivot grab at end of reversal)
DACUS is missed, but I don't think Jigglypuff actually has a fundamental issue with away rolls. Similarly, I don't see slow jump squat as an issue; you are supposed to want to
stay in the air as Jigglypuff, it's mechanically consistent for the
transitions to be something you seek to avoid. I'd sooner improve dash attack and her aerials to improve her in either of these areas respectively.
Stop talking about Sing. Yes, Sing is useless,
but the game is better off for it. A Smash Bros. in which Sing is a good move is a bad game, it's the type of move that is destined to be either useless or heavily abusive, and frankly just shouldn't exist.
Also stop talking about Yoshi's air speed somehow making Jigglypuff worse. Yoshi's airspeed only affects Jigglypuff in one matchup, and that's Yoshi. Yoshi has better max horizontal air speed than Jigglypuff, but is worse in every other category. Wario has better horizontal acceleration too, but is also worse in every other category.
Jigglypuff is still the overall aerial movement queen, and arguing over isolated exceptions is avoiding the real question of "Why isn't Smash 4 Jigglypuff able to leverage her aerial mobility advantage into a potent neutral?"