Best 5:
1) Professor Layton (the most likely third party addition at this point, and with the other three third-party fighters as default characters, I think Layton would be a fantastic "final unlock" character.
2) Descole (He is Professor Layton's villain in the prequel trilogy (Last Specter, Miracle Mask, Azran Legacy), and I know his chances of getting in are slim like Tails or Zero, but I already have a great move set idea for him, and he can be a really good surprise character, being another one of those "final unlock" characters. Again, its my preference, and if I saw him on the roster, I'd ecstatic. In addition, b/c Layton's games were tremendously successful in the DS era, he can be worthy of two newcomers, and it could also be a perfect last hurrah for the franchise now that the Layton is no longer the star. He'd also be a great way to promote the series' prequel trilogy).
3) Bandana Dee (the most likely Kirby newcomer, and he is starting to become an iconic character in the franchise along with MK and Dedede. He can be a unique fighter thanks to his spear)
4) Impa (She's definitely become a much more iconic character these past few games, and I see just so much potential in her).
5) Marshal from Rhythm Heaven (since the chances of Chorus Kids appearing in the roster is pretty slim at this point, I could see him getting in their place. I too am supportive for a Rhythm Heaven rep).
Worst 5:
1) King K. Rool (I would prefer Dixie Kong getting in more than him, especially since he hasn't a had a major appearance in a DK game aside from Mario Super Sluggers)
2) Ridley (Yeah, I am one of those people that don't doesn't support Ridley as a playable character, and I am personally convinced he really is the Stage Boss of Pyrosphere, so seeing him on the roster wouldn't make me happy)
3) Dark Pit (personally think he was better off as an Alt costume for Pit)
4) Dr. Mario (I'd prefer Mewtwo as the Melee rep, and he is a rather unnecessary Mario rep. Bowser Jr and Rosalina are good enough)
5) Singular Ice Climber (The ICs charm was being able to use two fighters at once, so seeing just one IC would lose a lot of value for what they are supposed to be in Smash Bros)