Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
Let this sink in for a moment: Mario Paint released in August 1992. Now, this isn't meant to make you Super Nintendo fans feel ancient (though I just made myself feel old), but to recognize that Nintendo hasn't released anything like it since then. But even as a piece of software—apart from the fly-swatting mini-game, can we really call it a game?—it had a basic drawing utility, a stamp maker, a simplified loop animator, and the infamous yet still-popular music generator with which you can hear Nintendo-rific covers of, say, the iconic Guile's Theme.
Finally, over two decades later the Nintendo-centric user-creation mega-widget returns in the form of Mario Maker, which so far already looks to be a fantastic level editor. Along the top of the screen is a hotbar of various classic Mario platforming elements that can be dragged and dropped anywhere on the field. Any mistakes can be swiftly undone by pressing the Laughing Dog icon from Duck Hunt in the lower left-hand corner.
The basic building blocks, breakable or unbreakable, form the environment with question mark boxes, mushrooms, and coins available to fill in the space. Pipes, trampolines, and moving platforms flesh out the rest of the level, while various enemies from goombas, koopas, piranha plants, and hammer bros prevent Mario from advancing toward the flag. Does that goomba need a piranha plant on its head? Why, yes it does. From there, you can play the level and examine how difficult you've made things, and you know users will seek to create the most insanely challenging levels known to man for your amusement. Something as close as possible to Unfair Mario.
Better yet, you can switch between either NES Super Mario Bros. or the more modern New Super Mario Bros. aesthetic, with more styles slated to come in the final release. It's my hope that Nintendo includes as many objects from Super Mario World as possible, since there are some "tubular" Star World specials in my head that have been waiting to manifest themselves for years.
The available demo I played at a private Nintendo showing had several restrictions, though, like needing to have the climbable flag at the end of the level and not allowing any pitfalls of any kind, so it's clear that Nintendo has a long road ahead of them before Mario Maker is ready. Online sharing has yet to be finalized and will need to exist in some capacity for the game to be treated seriously. A music editor is planned to be included, but there's very little information about it. The developers are flirting with the idea of a 3DS version as well, but nothing has been announced so far.
Mario Maker for Wii U will arrive in the first half of 2015.