Well, crap... Apparently, there's only 16 playable rangers. Which is crap, since there's been, like, a billion of them.
Going by the list at
Wikipedia, there have been 116 different Rangers. Now, this counts such one-shots as in the episode where there are (good) robot versions of 4 of the five main rangers or the "Wild West Rangers" and counts rangers who served in different periods (Say, Tommy as Green, White, Red, Black) as different rangers. It also counts the Rangers as different if, say, the costume and generation stayed the same, but the character left (for whatever reason, say when Jason was replaced by Rocky in the first generation). It does not, count the evil clone rangers that made various appearances throught the show. It does, however, count evil clone rangers who went on to become Rangers for the force of good (Tommy's clone, in particular).
Trimming the list down by skimming over the second half of the above list, it appears there are about 80-90-ish "regular" Rangers.
And we get 16?
Disney needs to make a new Power Rangers fighting game with just crap tons of Rangers and Villians. Wait, scratch that. Disney needs to outsource to the Soul Caliber team to have them make this game. With all the characters and weapons, it'd be interesting to see what the SC team could do with this. And I'd love for it to turn into a "real" fighting game where people play it at tournaments.