Lol so if ninten came into the game he'd automatically be better than Ness? Great logic.
The joke is that Ness actually became viable in smash 4. I don't even understand at this point how you decide your mains from game to game.
Sorry, reading comprehension: "Ness is the weakest Mother protagonist (character)". That is to say, his character, to me, is the most poorly developed of the protagonists in the series. Stats wise? I'm pretty sure he's actually the strongest. I guess theoretically, since Lucas doesn't suffer asthma or have much of a home to be homesick for, he's the strongest, based only on potential successful damage output. I digress.
"Better", "good" and "viable" are states of mind. If Ninten were to suddenly replace Ness, I would have to agree that statistically, he's better than a character who isn't in; I think you would too. Even so, if he were added, I would love him and be more inclined to play him over Ness. Given the option of a free set win with Ness, or guaranteed set loss with Ninten, I'd pick Ninten - I just like him more. I love the Mother series, my maining Ness in 64 and secondary in Brawl are just reflections of that.
Likewise, given the option to have whatever makes Ness viable, and playing Lucas, I choose Lucas, because I like him more. How I decide my mains doesn't even seem to be hard to understand, unless you're being willfully ignorant of it: I pick from who I like. It becomes a harder choice as the roster grows, but in the end, when you compare love for a character to understanding of a playstyle, it narrows it down.