Or less intellectually phrased ''one just released yet another instant classic game, the other is almost down to lower their inexistant trousers to please the furry scene''
Simply said, at the birth of the proper multi-console system (the release of the Genesis in 1991, I would say), the flagship franchises were Sonic and Mario. Thanks to a CharlieSheenesque succession of bad decisions, one franchise essentially peaked in 1994 (Sonic and Knuckles) and the other is still able to carry entire consoles production lines in 2017.
While ''rivalry'' in console franchises/consoles might not be the best term (brand loyalty, maybe ?) you can't help to fathom how one franchise managed to survive through, what, four consoles generations ? while their arch-rival in platforming best outing in years was ''yet another remix of levels from Sonic 1 to 3, but not much beyond that''
(That thread is not really asking a ''question'', just the bafflement of someone whose first console was a Genesis in 1992 about how every Mario game is revered while virtually all 3D outfits of Sonic are broken messes and 2D outfits at best derivative fanservice from the 3 classic Genesis games. Mario Odyssey is a masterpiece and Sonic Forces (groan) is competing with the reboot of Bubsy.