I have my own tiers… and I am including an "S Tier."
The way I set up my tiers involve character slots, the options a series has, critical reception, and sales.
S Tier:
-Mario
-Pokemon
These are two of Nintendo's best selling franchises and are two of the best selling video game franchises of all-time. In terms of character representation, these series will most likely get the most characters. Mario already has a 5th slot again with Rosalina, but Bowser Jr. seems to be a likely candidate for the 6th slot. Pokemon already has good characters that don't deserve to be cut and Mewtwo is by far one of the most requested characters worldwide. Pokemon might get a 6th slot from a Gen 5 Pokemon, Zoroark perhaps. They will get 4-6 slots.
A Tier:
-The Legend of Zelda
Strictly Zelda. This series has some good option for slots and is a series that Nintendo emphasizes on. Often draws in crowds, gets good reviews, and gets some pretty good sales. However, it's arguable if this series will get a 5th slot. Ganondorf is guaranteed while other characters, like Ghirahim and Toon Zelda, are fighting for a 5th slot. I see about 4-5 slots.
B+ Tier:
-Donkey Kong
-Kirby
Two series with great sales and have great followings. Donkey Kong is placed higher for having 2 tremendously good options in King K. Rool and Dixie Kong. These two might get their own slot, but one might come out with one. Kirby also has a good option in Bandana Dee, but fans argue whether or not the series is fine with the main trio or should have Bandana Dee. I see 3-4 slots here.
B Tier:
-Fire Emblem
-Star Fox
Fire Emblem would be lower had it not been for Awakening. Ike is still a rather popular character and might come back. While people want Chrom and Roy, Fire Emblem is not as big or as popular as Kirby or Donkey Kong, so it will only get 3 characters max. While Star Fox is definitely losing popularity, it gets here for the fact that it has a 3rd spot alone. It might live to see a cut or have both Falco and Wolf. Krystal getting her own slot is highly questionable. Star Fox is ranked lower than Fire Emblem because it is more likely to get a cut rather than a character. I see these series get 2-3 slots.
B- Tier:
-Kid Icarus
-Metroid
These series definitely draw in some crowds. Kid Icarus is placed higher for the fact that if has two extremely good options with Palutena and Hades or Medusa. Palutena also has worldwide popularity. Metroid is placed below because the only really good option here is Ridley, but Dark Samus seems popular. Any other character might get in, but chances are rather low. I can see these series stick it out with Pit and Samus only. I see these series get 1-3 slots.
C Tier:
-Animal Crossing
-Pikmin
-F-Zero
-EarthBound/Mother
Animal Crossing is also a rather popular series and it's possible that it could get two candidates, but I can only see the Villager get in solo in this game. It is ranked higher for getting a character already. Pikmin 3 is currently helping the Wii U right now and it is a series that Nintendo is recognizing. 2 characters here are not out of question, but they don't seem very likely. It could be a good series to get a second candidate for the next game as it has Louie and Alph. F-Zero is placed below as it definitely has two good options as well with Black Shadow and Samurai Goroh; both these characters have some demand. However, seeing the state of F-Zero, getting that second slot is unlikely. Outside help to revive the series will probably help get that slot. EarthBound is on here for the simple fact that it already has two slots. The series may live with a cut, but EarthBound on Virtual Console helps Ness not get cut. EarthBound is ranked lower for most likely getting a cut rather than a character. I see these series get 1-2 slots.
D Tier:
-Wario
-Yoshi
-Game & Watch/Ice Climber/Robot
These series have one clear candidate. Wario and Yoshi are highly unlikely to get a character. Wario is more likely for having more options, but Wario seems to represent the series just fine and no one from WarioWare or Wario Land stand out. Yoshi is just fine with Yoshi alone and the Baby Mario Bros. and Kamek seem like longshots. The other series are retro; I would be surprised if they got a second candidate. These series will definitely get 1 slot alone.
E Tier:
These include other series like Wii Fit, Xenoblade Chronicles, Punch Out!!, Golden Sun, Mysterious Castle (Takamaru's series), Wii series and among others. They all have deserving candidates, but only the frontrunners will get in. Depending how things go for Xenoblade in the future, I can imagine it going from E to possibly C if X is a Xenoblade sequel and if the series will have a future beyond X. While the Wii series is by far one of the best selling series for Nintendo, the only candidate is obviously the Miis, so it ends up here rather than getting higher on the list. These series will have no slots or just one.
