Did Donkey Kong actually come out on the 2600? I would have imagined Nintendo would have shut it down, like they did id software's Mario Bros PC port.
I think that Atari also did the PC version later on, which was largely a mechanical translation of a cartridge implementation (might have been the 400/800 version, don't really remember -- I only know that I never got any royalties or bonuses, and that many other people did).
As recently as two Fridays ago.
That said, the 2600 version (and Coleco version, which was basically the same thing) was incredibly popular.