Me too, it is a shame when Sales dictate the system eh?
If that is not enough, here is a list of other things Pokemon has going for it:
-Easy translation into smash fighters
-Huge marketing capabilities (to draw in more fans, as well as by Game Freak, seen to get Smash fans into Pokemon)
-Vast Empire (Manga, TV, Movies, Trading Cards, Figures, Apps, Clothing, Merchandise beyond compare)
-800+ extremely diverse characters
-20 Years of history
-Worldwide Popularity
-Many types of characters it could represent beyond the basic Pokemon (trainers, rangers, breeders, coordinators, etc)
-Much in the main games to represent (abilities, items, weather and battlefield, double/triple/horde batles, typing, gender, contests, sports competitions, happiness, personality, trading, evolution-all different ways- etc)
-Multitude of types of games to choose from (Main RPG, Ranger, Mystery Dungeon, Snap, Pinball, Trozei, Puzzle League, Coliseum, ... the list is endless)
Sales are not the only factor. Popularity, Size, History, Impact, Relevance, Recency, Diversity, Adaptability, Growth.
Pokemon is unlike ANY other video game franchise, because it is far more than a video game franchise- it is studied on global economic trends as a phenomenon which is still not fully understood on a consumer trend and has not been replicated to this day.
How many reps does it deserve? Well, a good number. It is certainly on a scale to be evaluated separately from all other franchises as it is in a category all its own. A Pokemon added will appeal to a huge audience, regardless of which it is- an audience likely bigger than another given character added. I would not be surprised if it got more than six representatives, not surprised in the slightest, and it would be more than warranted, it would be earned.