Well, since we're gonna be here for a while, probably with nothing new to talk about...
What's the dumbest reason to exclude Ridley you've ever heard? Don't say "too big" because that's too easy.
I think my favorite is "he's too powerful." When Mewtwo can make people's heads explode and Ganondorf has the Triforce of Power. Plus, if Samus can beat Ridley single-handed, wouldn't that make her even more powerful than he is? Why aren't we excluding Samus from Smash on this basis?
"he's not as relevant of a Nintendo character as other veterans and newcomers are. he's not important and I don't know why they would put him in Smash."
... allow me to go on a tangent.
I allow Nintendo a total of one maverick attendee per Smash.
in SSB64, I would say the maverick attendee title really could've been up for grabs between Captain Falcon, Ness, and Jigglypuff. Jigglypuff isn't as iconic or relevant to the Pokemon franchise as Pikachu; EarthBound is certainly a fantastic game (my favorite RPG, if not my
favorite SNES game, if not one of my
top three favorite games) but since he only appeared in one of two Mother titles, I would say his inclusion is a little iffy. Captain Falcon is much the same, although he's more of a veteran in his own series than Ness was.
in Melee, it was Ice Climbers. no one remembers their game. I could justify every other Melee newcomer except for Ice Climbers. in Brawl, it would be Pit for the same reasons.
in Smash 4, I would say that so far there are no maverick newcomers. Wii Fit Trainer could be argued as being a maverick, but I say her inclusion is the same as ROB and Mr. Game and Watch- both were historically relevant characters to Nintendo's success (ROB got the NES sold, the Game and Watch was Yokoi's first foray into game design, Wii Fit appealed to the casual audience and helped sell units)
Villager... could be a maverick, but Animal Crossing: Wild World had a stage in Brawl. so I think his inclusion was inevitable.
when people say Ridley isn't 'relevant' I think of the maverick characters I listed. I would consider them irrelevant, excluding Pit because he's been revived (and, incidentally, is canonically the strongest Nintendo character according to Kid Icarus: Uprising).
Ridley, percentage-wise, has more of a recurrence ratio than Ganondorf, the most iconic Zelda villain. Ganon, in any form, has appeared in only five out of 17 Zelda games, six if you count linking the Oracle games- The Legend of Zelda, Link to the Past, Ocarina of Time, Wind Waker, and Twilight Princess. Ridley has appeared in Metroid, Metroid: Zero Mission, Super Metroid (and fought twice), Metroid Prime, Prime 3: Corruption (fought twice in that, too), Fusion, and Other M. he's been in seven of ten Metroid games and been fought nine times over the course of Metroid history, and even been featured on the boxart of a few of the games. I fail to see how he isn't 'relevant' as a character, in terms of Nintendo villains or Metroid canon.
I get very passionate about my franchise and I defend it with about as much honor and dignity as I can when faced with the ignorance and oppression that is the anti-Ridley establishment.