In Brawl it was understandable, not only did they have 18 new characters to make, but many of them were admittedly much more important to Nintendo than Ridley is. This time, there'll be less newcomers, which could give more time to make such a difficult character as Ridley. All the stars should be aligned in Ridley's favor this time around...
This has me thinking...
What if the key reason for Sakurai not considering a playable Ridley is that he doesn't see Ridley has having enough star power??
I mean obviously we'd think "That's ridiculous!" But I keep saying that it's likely Sakurai doesn't truly get Metroid. By this I mean his knowledge of the series only goes so far as to ensure a certain level of authenticity when trying to bring it to Smash. He knows Samus is the hero, he knows of Zero Suit Samus, he knows of various enemies she has faced such as Kraid, Ridley, and Mother Brain. He knows some places like Brinstar and Norfair and Frigate Orpheon. And he's done a little extra research here and there to develop trophies.
But we all know Metroid doesn't exactly grab the attention of people in Japan. Sure some individuals may still enjoy the series. But who's to say Sakurai is one of them? I doubt he is. On the other hand we know Sakurai likes the Star Fox series, so I wouldn't be surprised if he knows a little more than a passable amount of info.
Point is, I wouldn't be surprised if, to Sakurai, Ridley was on the same level of importance as Kraid: One of two strong enemies Samus has faced before. Ridley may have shown up a lot more since, but maybe it's because Kraid is so big that it's implausible to see him just anywhere. Ridley did kill Samus's parents, so he's especially hated by Samus. He also leads the Space Pirates.
Without being aware of the implications of Ridley's actions, his status, and his prevalence throughout the series, I can believe that a person might conclude that, compared to other villains like Bowser and Ganondorf and Dedede, Ridley's influence and importance to his related series is only moderate. And again I think about Star Fox; Wolf couldn't be compared to other Nintendo villains (him even being a villain is questionable). But Sakurai is likely more familiar with the series and thus better understands Wolf's role.
So with Wariofan1's words, who exactly was "more important" at the time? The sure bets are Meta Knight, Dedede, Olimar, ROB, Diddy Kong, Wario, Sonic, Snake, and Pit. These guys play a major or top role in their series. ROB in particular represents a past era.
It's the other's that I find more questionable.
Lucario - Popular pokemon mascot of the moment. Priority is relatively short lived
Pokemon Trainer - Represents the primary role players take and 3 very well known pokemon. Arguably very important
Lucas - Important, but to a single game (I believe)
Ike - Same as above
Wolf - Rival status, not a main villain, arguable
Zero Suit Samus - A different form of Samus. Important, but higher priority??
Toon Link - Sakurai is apparently adamant on having a young and adult Link, so priority may be his own preference
To I and others who understand Ridley's importance, it would seem that Ridley at least is on equal grounds with some of these. But to somebody less familiar with the series, maybe Ridley falls below these expectations. I've said before that a Nintendo character needs at least one of these qualities: The "All-Star" that's practically the face of the series, the "Co-star" in which most people immediately identify with the series, and the "Era guy" who draws attention to a specific Nintendo era. Thanks to the lack of familiarity, one could think Ridley fails all three of these prerequisites.
There seems to be two key goals that we as the Ridley fanbase may have failed to focus on simply because it didn't come to mind.
1 - We needed to further emphasize how important Ridley is to his series. We're fans. We know the reality. But just making Ridley very popular seems to mean he gets past "Trophy" or "Background appearance" status.
2 - We should have promoted Ridley post E3.....
2012!! Even sooner than that. Maybe some of you did. I certainly didn't notice. But I don't just mean lots of discussion and arguing ('cause the detractors join the ride). Could you imagine if we took to Twitter and stuff about Ridley as soon as Smash 4 was mentioned?
I dunno. Maybe #2 did happen and I myself just failed to jump on the train.
Also, could you imagine if this post had a character limit? Then I wouldn't allow my thoughts to balloon this post to this size and require a ...
TL;DR version - Sakurai may not truly acknowledge Ridley as a genuine all-star on the same levels as other villains like Bowser and Ganondorf due to simply not having enough knowledge of the series. It's arguable Ridley wasn't as important as most of Brawl's newcomers. Maybe if Ridley's fanbase better emphasized Ridley's importance, Sakurai would look at him differently.