Still, not a bad track record for a character whose storyline makes absolutely no sense.
The Guardian has a list of 25 facts about the character to mark to faux-anniversary. On the long-standing beef between Donkey Kong and the Mario family I come down firmly on the side of the monkey. So my favorite of those facts is #5, reprinted below:
5. Donkey Kong Jr, the 1982 sequel to Donkey Kong, is the only game in which Mario officially stars as the antagonist. He has trapped poor Donkey Kong in a cage and the ape's son must rescue him. In the game's promotional material, Mario even gets a specially twirled moustache, highlighting his evil nature.