I really don't buy a lot into representing or overrepsenting because if we wanted to be fair based on sales, Mario and Pokemon should just dominate the game, especially Mario once you factor in his platformers, rpgs, Mario Kart, and all the party/sport games.
However, the problem with DK getting 5 is that after DK, Diddy, King K Rool, and Dixie Kong, their actually isn't a lot of options. You could go with one of the DK64 characters, Donkey Kong Jr. (which is actually the current DK), or a generic Kremling but they would be a stretch. Funky Kong is popping up more in Mario games but he too is a stretch.
Not much in DK realm to choose from after those 4.