A reader writes:
Mickey Mouse is more iconic because he was created over a decade before Bugs Bunny, and several of the cartoons he appeared in represented real technological breakthroughs – milestones in the development of sync sound and color and multiplane animation etc. By the time Bugs came around in the late 1930s, the idea of anthropomorphized talking animals appearing in colorful sync-sound cartoons was fairly commonplace, and Mickey typified the form.
Also, Mickey was the first Disney character to catch on, so he became a symbol of Disney as a whole. Meanwhile, the animation studio at Warner Bros was kind of the red-headed stepchild of the operation. You couldn’t mention Disney without mentioning Mickey, but Warner Bros was much more interested in promoting its human stars. WB's flagship characters weren’t Bugs and Daffy; they were Bogart and Bacall and Bette Davis and Errol Flynn.
Another reader provides further detail:
Cartoons were an adjunct to Warner Bros. vast studio operation – indeed, before the 1940s, they were actually produced by an outside company (Leon Schlesinger's outfit) and not even located on the Warner lot. Cartoons, on the other hand, were the raison d'etre of the Disney operation well into the 1950s. Warners sold off its pre-1948 animation library to a TV distributor in the early '50s, keeping only the increasingly inferior late product to itself. It only regained ownership of that material when it acquired Turner Broadcasting. Disney, again, maintained control, ownership, and usage of its cartoon library all along, using it on TV shows like "Disneyland", "The Wonderful World of Disney," and, of course, "The Mickey Mouse Club."
Bugs only became an important part of Warner Bros.' image when brand marketing became important in the 1970s; Mickey was Disney's "spokesmouse" all through the Baby Boomer era.
Another is more succinct:
Mickey Mouse may be more famous as a corporate icon, but he’s far less popular as a character. The McDonald’s arches or a Coca-Cola logo are more recognizable than Bugs Bunny as well. That doesn’t mean you’d want to watch them for half an hour.
Artist Wouter Klein Velderman is creating the above sculpture:
I decided to build a Mickey mouse in Moengo, [Suriname] completely made out of wood. It seems like the country of Surinam is in some sort of transition. … Mickey Mouse counts as a symbol for a certain kind of transition – the progression of Western society.
The Dish 