People will hate me for this, but I think Brawl's a better competitive game than Smash 4. Smash 4 feels like it's trying to play the threshold between casual and competitive, but the result is a game that fails on both fronts.
There were actually more true combos in Brawl than there are in Sm4sh. This is due to the fact that many moves have either been given the Melee Knockback (0 BKB/100 KBG), or the new, Sm4sh Knockback (100 BKB, X KBG), and when combined with the universally slower animations (which were slowed in an attempt to make the game appear more "dramatic"), it creates a situation where only 2-piece combos are possible (if even that), and most "combos" are simply tricky frame traps. In addition, all standard attacks have been significantly nerfed in damage, while Smash Attacks have been significantly buffed (in both power and speed), which promotes a campy, spam-based playstyle. The gameplay also feels more restrictive; due to the emphasis on dramatic gameplay, the camera has been moved to such close proximity that one often can't even see the whole stage, this claustrophilic camera, added with the stiffer (and possibly slower?) air speeds (Maximum H Air Velocity), and combined with the higher (yet insufficiently so for competitive gameplay) gravity values creates a feeling of Smash 4 being more of a "stiff Brawl" or "faux Brawl" than a unique, genuine product.
Also, I'd honestly take Bretaknight, over Bayonetta. Regarding them, even if Metaknight is hypothetically better (at top-level gameplay), Bayonetta is better at low-mid gameplay, while still being the best top-level character relative to her respective Smash game. A casual MKnight will get destroyed by an experienced player, but anyone can pick up Bayonetta and get results.
Metaknight will always win the neutral. If Bayonetta wins the neutral, she will always win the game.
Two characters who are equally as bad, but in different ways. People say not to compare them, but Bayonetta's 0-deaths are much more reliable than Mknight as her opponents don't have broken DI/SDI to help them escape. You rarely (if ever) see Metaknights 0-death people at top-play, however Salem 0-death'd ZeRo multiple times as his Bayonetta. Does this make Salem bad? No; he's simply playing to win, and Bayonetta is the means to that.
Digression aside, besides from ICs, and possibly Snake/Metaknight, Brawl was relatively balanced. Yes, Diddy Kong and Dedede (as well as a few others) had infinites, but the matchups never felt hopeless.
Another problem with Smash 4 is that there are no viable AT's. This also means that the skill gap is much smaller, and the skill cap much lower. A character is only viable to the extent that their default kit allows them to be. This means that if Mewtwo is cumulatively worse than Falcon, for example, his inferiority is static. In Brawl, Dedede wasn't that viable alone, however his infinite helped make him a notable threat, same with Falco, a character who, off his own kit, was subpar, but with chaingrabs and DACUS, became a contender.
Smash 4's Hitstun is another example of it playing the line; In addition to it being slightly lower than Brawl's (which is equal to Melee's), it also retains it's cancel-properties, which are now KB-Dependent. This means that Hitstun-Cancelling never left upon the transition from Brawl to 4, it merely changed. This often leads to situations where characters are stunned for short enough periods to allow interruption, but not long enough to have feasible chances of escaping, which is responsible for all of the Frame-Traps and resets in Sm4sh, which is honestly worse than Complete/Absent hitstun. The illusion of hope is far worse than it's presence or absence.
The Final thing (for now) is another massive problem Smash 4 did, which is called Neglectful Balancing. This is where developers immediately nerf characters perceived to be overpowered from prior iterations, while gradually buffing the surrounding cast to accommodate a threat which no longer exists. This can be clearly seen with characters like Olimar and Game&Watch; two characters that were butchered--compared to Mario, Sonic, and Charizard, for example, who were "significantly buffed". Considering the state of the roster, Brawl&Watch and Brawlimar would've likely been balanced inclusions to the roster, but now they are but joke characters who nadie plays. I'm also rather upset that they Standardized Mewtwo. He feels to basic in this game.
So how do I feel about Brawl? I feel that Brawl was a decent game. Certainly not better than Melee (competitively speaking), but it's definitely better (collectively) than the other iterations for varying reasons. Casually speaking, Brawl was the best game, slightly surpassing even Melee. Artistically speaking, it is apparent, when analyzed, that Sakurai still cared about the franchise during this point; Brawl was a very personal and intimate game. Smash 4, however, feels like it was made by Nintendo (a company) rather than an actual human being. It feels like a "product" instead of a "project".
And regarding potential; Brawl has the most potential out of all of the Smash Bros. games. A combination of hackability and internal accessibility allows Brawl endless hacking possibility to be anything that one desires it to be. Brawl is the core of Smash; having a unique identity, while simultaneous being able to assume the properties of it's counterparts. Whether it be 64, Melee, or Wii U/3DS, with enough time and knowledge, Brawl can become those very games, and expound on them in such a way that they themselves cannot do alone. Brawl is a masterpiece inhibited by the contempt of it's creators, but through hacking, the light, which has for so long been concealed, can finally shine, as intended.