Here's who I would add if designing the roster were up to me. Now you can see why I have no business being involved in such a thing...
1. Isaac (Golden Sun) - Forever my most wanted character until he finally gets in. Love Golden Sun.
2. Mach Rider (Mach Rider) - I'm still not sure why I want him so much as I've never played his game, but I just feel like he'd be a super unique addition.
3. Andy (Advance Wars) - I'd love to see some more Advance Wars representation in Smash. It's a neat little franchise with lots of charm.
4. Ken (Street Fighter) - I prefer him to Ryu, and I'd like some more Street Fighter representation.
5. Porky (Earthbound) - If we were to get another Mother rep, it should definitely be him since he's in 2 of the games. Also it'd be nice to have a Mother rep who didn't rely on PSI. He's also one of my favorite game villains too.
6. Frogger (Frogger) - One of my favorite game series growing up. I'd love to see Frogger get a resurgence, and Smash could give him that chance.
7. Chibi-Robo (Chibi-Robo) - Honestly kinda surprised he hasn't shown up yet. I'd settle for him being an Assist Trophy at the very least.
8. Ninten (Mother) - As much as I love the Mother series, I've never really been dying to see Ninten playable... But, I wouldn't complain if he was...
9. Mike Jones (StarTropics) - I love retro reps, and even though I haven't played his game, I'd love to see Mike Jones on the roster.
10. Captain N (Captain N: The Game Master) - Would probably be the funniest, most "WTF?" addition in Smash history. If only it could happen...
11. Raiden (Metal Gear Solid 2) - My favorite Metal Gear character besides Snake. I'd take him as a MGS2-styled Snake echo or as the cyborg ninja version from MGS4/Revengeance. Just gimme.
12. Proto Man (Mega Man 3) - I always liked Proto Man more than Mega Man for some reason. He could be a pretty easy echo for Mega Man too.
13. Shovel Knight (Shovel Knight) - I'm happy my favorite shovel boi got in at all, but I'd still love to see him playable some day.
14. Soma Cruz (Castlevania: Aria of Sorrow) - The coolest non-Belmont from one of my favorite Castlevanias. If they were to add another Castlevania rep, it should be Soma. His moveset would be awesome, since he can use Souls to command monsters.
15. Shanoa (Castlevania: Order of Ecclesia) - I think Castlevania is a deserving-enough franchise, and I think Shanoa's got a pretty unique fighting style compared to other protagonists in the series. She could also use her Glyph magic to augment herself with additional weapon powers. Plus she could break up the Castlevania sausage fest.
16. Tails (Sonic the Hedgehog) - I love me some classic Sonic games, and Tails would be a much better fit for Smash than Shadow IMO.
17. Skull Kid (TLoZ: Ocarina of Time) - TLoZ deserves a new rep regardless, but I'd like it to be him.
18. Ryu Hayabusa (Ninja Gaiden) - One of the last big series that I can think of that got its start on the NES. While not my most wanted by a long shot, I think he deserves a spot. Plus he could bring a lot to the table in terms of moveset.
19. Elma (Xenoblade Cronicles X) - If we were to get a new Xenoblade rep, it should be her.
20. Reckless Safety Notice Man - All right, I did say Captain N would be the funniest addition, but this guy would be pretty hilarious too.