Nobody gave a crap about Ice Climbers, and even back in the day it was pretty panned and considered one of the weaker NES/Famicom launch titles.
As awkward as those jump mechanics may be, do remember that the main programmer considered it a warm up for Super Mario, which, yeah, don't need to explain that. Quite a few Nintendo folks got their start on it, actually. I also consider Ice Climbers to be Nintendo's first cooperative multiplayer game, as I see the only other multiplayer game before it (Mario Bros.) to be more of a competitive game.
As for what makes for a better roster, I'd say being able to connect with the character trumps all. Being able to make folks like a charter, allowing fans of the old ones to enjoy all the references while attracting a new audience, determines if a character succeeds or not. I don't care if you have the best, most ballenced moveset ever; if you can't make folks enjoy that charater, they might as well not be in at all.
Do keep in mind, however, that move set matters little in how much a person cares about someone. Look at Roy for proof: that "inferior last-minute Marth clone" still has a vocal, dedicated fan base even after being cut out.
Let's look at Lucas and Ness to see what I mean. Lucas has a number of taunts that don't exactly feel taunt worthy, tripping and being bitten by the Rope Snake. A larger number of moves revolve around the psychic powers he has, which more often than not have more lag than Ness's. Even his Neutral Special is harder to hit with. Lucas, then, is characterized as being weak and cowardly, and tries to inspire sympathy from an audience who wishes to protect him. This is a large contrast to Ness, who seems braver and more certain of himself, ready to take on the world with whatever comes his way with anything (namely, that bat and yoyo).
I could go on and on for countless "similar" characters here. Heck,
I've already done it. Not once,
but twice. In fact, with the reveal of Toon Link, I think this is what Sakurai means by having characters "unique." Even if they aren't that different, they
feel different enough that people will like them anyway.