Spawned by the Super Mario Bros games, 2D platformers were a wildly popular genre of the 80s. There were hundreds or thousands of different platformers across all systems, from consoles to handhelds to arcades to home computers to PCs and Macs. Every console manufacturer needed a platform mascot like Mario. Their popularity has faded since then (just like the popularity of point'n'click adventures). This can partly be explained with a changeing audience, but also with new technological possibilities. The art of game design has moved on, reprises like the New Super Mario Bros not withstanding. 3D platformers are not the same genre at all (it just so happens that Mario went from one genre to the other) and they are certainly not as dominant today as 2D plaformers were in the 80s and early 90s.
Hardcore gaming is a bubble economy blown up by Microsoft's $7 $6 billion losses.
