PSABR was actually very good and very fun, and it did attract quite a number of fans. I wouldn't call it a complete failure, but a semi-failure, semi-success.
It succeeded in being an actually fun alternative to Smash. If someone was playing Smash with me for a while, but got bored and wanted to switch to PSABR, I wouldn't mind at all. It's a fun game that I really wouldn't mind playing, and there is depth to it. Sure, it's not super fast like Melee, but that's not what fighting games have to be about. PSBAR has it's own kind of depth to it and you can pull off insane combos if you practice. I still don't think it's as deep as Melee, but I do think PSABR is the much better choice for those who would rather play a more strategic game, without all of the split second inputs that are required for Melee competitive play. PSABR has objectively better teaching tools for it's competitive play too, meaning it's a lot easier to get into than Melee, where the majority of advanced techniques are not actually taught to you, but are the result of exploits in the code that were either accidentally found and left there intentionally by developers, or were never found at all, and just slipped through testing. Nobody can deny that to get into Melee's competitive play (or Smash's in general), you have to do a lot of online research, or you have to live in a community with a competitive scene that would allow you to discuss the game and it's advanced techniques. The game has tools for practice, but not for actually teaching you anything beyond the basics. PSABR went to great lengths to teach you how to play at an advanced level, and it even had a few sample combos for each character that taught you how their attacks worked when it came to linking up different moves. And even forgetting the competitive side, it's a very fun game to just casually play with friends. The items are fun to use, and the stage hazards are actually really cool.
I also think there are a few other things that Smash could learn from PSABR. For example, the ability to turn stage hazards off. I read one interview where Sakurai scoffed at this idea (then again, his response was vague, so maybe he didn't mean it in a snarky way), but I wholly disagree, the ability to turn stage hazards off would be a god send for competitive Smash (though I know Sakurai doesn't think too heavily about the competitive scene). Due to the strict rules of stage legalisation, the variety of stages I could play on in a Smash tournament is very tiny. In fact, the universally legal stages across all three Smash games is less than the amount of stages in PSABR. And after doing a quick check, PSABR's stages are generally considered to all be legal because you can turn off the hazards.
PSABR also had a neat mechanic that allowed you to control which direction you faced after performing a dodge roll, while Smash forces you to face a particular direction depending on what type of roll you use. I think a mechanic like that would be a nice addition to Smash, and I'm sure competitive players would be all over it, as it increases the options you have when coming out of a dodge roll.
I also really liked the "Rivals" idea and the little cutscenes the characters had, and while I won't bet on it, I really would like to see something like that in Smash 4.
And of course, PSABR had alternative costumes for each character, multiple ones in fact. And that's on top of the standard recolours we are used to in Smash. I really feel Smash has no excuse not to have this feature at this point, it was really teasing how only Wario, Pikachu, and Jigglypuff were the only ones who had them in Brawl.
However, PSABR failed in the sense that it failed to have many key characters. While it did surprise me in bringing back classics like Parappa (complete with his original voice actor), and Sir Daniel, and had pretty much all of the key reps from the PS2 and PS3 era (and adding Kat from Gravity Rush as DLC was also a neat move, as she is a really cool character and her game is awesome), it was missing key characters from the PS1 era, mainly the likes of Crash, Spyro, and Tomba. The third party reps were also very odd choices for the most part. The only ones I thought made sense were Heihachi and Raiden (who was an understandable replacement for Snake). And while I understand that this is not the fault of the developers and is due to complicated licensing issues, it still was a huge shame, and the third party reps they got felt like they had little to do with Playstation, for the most part.
It also was being developed by inexperienced developers, and while they did very well, it doesn't compare to what veterans like Sakurai can accomplish, which is why the game's balancing was so debatable and needed so much patching. And while it did well enough in terms of the AMOUNT of people who bought it, meaning a lot of people liked it enough to buy it, Sony spent more money on the game than the sales justified. Kinda like what happened with the Tomb Raider reboot.
