I must say that I give major kudos to those of the younger generation who respect our heritage, though I actually did grow up with K. Rool, myself. (My god, was that really twenty years ago, already...?
Yeah, I wasn't kidding when I said I was there at the time with the really old TV shows, either.)
A lot of people have been supporting him since the time of Melee. I remain amazed that he wasn't in by then.
If you're curious as to why he's popular, I can only shed light from my own perspective. I like him because he's a genuinely evil and competent bad guy, and he has numerous idiosyncrasies that make him memorable. He left a major mark with his pirate persona in particular, for me, though he has several (king, pirate, mad scientist, and boxer) - all of which, in the self-aware nature of Rare's DKC trilogy, poke good-natured fun at video game final boss tropes (as a mad scientist, he even ended up poking fun at a then-rival company's work, by using DK and Diddy as a power source for a giant robot).
He's also totally unhinged to go along with his evil tendencies - the first thing he did as a villain was to try to guarantee future success by attempting to starve his foes to death, and he only got worse (and more insane) as time went on - he beats up DK with the butt of his blunderbuss in DKC2, for example. He was toned down a bit in the DK games that were made by Paon (I think some have termed this "Bowserfication"), but even so he was no less competent.
This competence, evilness, and craziness, coupled with the huge amounts of things he did as a final boss, are what makes him an appealing candidate for a fighter.
This is like saying that Bowser shouldn't have gotten in before Rosalina, Daisy, Baby Mario, Baby Luigi, and Pink Gold Baby Rosalina. By this logic, we should have no villains, major or minor antagonists, or even people who merely looked at you funny one time in the series at all yet.
I'd love for Dixie to be playable too, but she wouldn't exist at all were it not for K. Rool's actions necessitating a sequel to DKC in the first place. I don't believe that a character introduced in a sequel is more important than a series' main antagonist who was not only there first, but also provides the impetus for most of the games to take place at all.
As for Cranky, I'm not opposed, but I do feel that making him playable completely misses the point of him, and it genuinely surprises me how often it comes up considering that he's popular specifically for the joke that he represents. The entire point was always that he was never a playable character himself in his
own games, and yet he preaches about how contemporary video game heroes should behave. That was always the joke behind Cranky. (For this reason, I have yet to be convinced that Retro Studios gets this.
)
This kind of reminds me of people's reasons for not wanting Dedede and the like in the Smash series. A character being fat really is not a valid argument. Though perhaps that's why Wii Fit Trainer's here? There are a few pudges on the roster, now.
That said, K. Rool is mostly muscle.
Anyway, I sincerely apologise for going off-topic here, but @
Hypernovaguy64
asked and wanted to understand, and I felt it appropriate to provide a detailed answer.