Size part was a joke... not a very good one apparently...
For the rest you, you got me there. Death never held any characters back, look at everyone who's gotten in to Smash so far. And about prominent characters, there's the thing, I don't see Medusa as as prominent as Pit or Palutena. (Divine Fighter's prominence depends on how much you played the amazing multiplayer). Sure she's been in almost all Icarus games, but how much of an impact did she leave on the series as a whole? It's really degrading her character to see that you had been chasing her down the entire time, just to realize that the entire time she was being controlled by Hades. It makes you think if you put all three games right after the other.
I hope you know I'm not hating on Medusa or you when I'm writing these, I'm just trying to explain why I don't think Medusa is a good choice. As for Kirby, King Dedede was planned since Smash 64, and Meta Knight has an extreme impact on the story of Kirby (even getting his own substory in K:SSU).
One more thing:
How much of an impact did she have? She was the main villain of the first game which was what MOST people played of Kid Icarus before Uprising, and was the most consistent villain of Uprising for the first third of it EVEN if she was shown up.
And sure Hades overshadowed Medusa in one game. But just recently?
- Ridley has been overshadowed in MOST games he is in by a different villain.
- Ganon in the last TWO games was overshadowed by Demise, and even more humiliatingly by Yuga.
- K. Rool has been overshadowed by Tiki Tong and Lord Fredrick who have outright replaced him through DKCR.
- How about the various games where BOWSER is overshadowed by the likes of Smithy, the X-Nauts, Count Bleck, Fawful, or whatever else in the two RPG series?
And you know as well as I do why Greninja, Robin, and Lucina are not good arguments. Fire Emblem has no unified continuity. They have no real choice but to use the newest games, because continuities generally end after one or two games with Archanea being the only exception. Pokemon also generally get in off new games alone, and Pokemon are always going to EXIST in the next pokemon game. That is literally always a guarantee.
As it sits now, Medusa is the villain of one game and the villain for the first third of another. Hades is the "highest" villain for a small fraction of the one newest game. As it sits now his resume just isn't great.
And Medusa is really only as much of a bad idea as Palutena would be.
I'm aware you're not hating on Medusa, but there really aren't BETTER choices with Palutena and Pit in the game, and Sakurai most definitely could exhibit the will to give us three Kid Icarus characters.
One new game overshadowing the series antagonist with a new one doesn't mean much. If Kid Icarus gets a new game where Hades is the main villain again, we can talk otherwise. Just how I see it.