In order to make games that aren't clones of well-known single-screen games like Tetris, Breakout, Concentration, or Missile Command, and in order to do so within the attention span of a homebrewer with a day job, one first needs to make tools to make games. An example of such a tool is the engine of a well-known game for the same platform. Romhacking.net has dozens of mods of Super Mario Bros., Super Mario World, and other games with editors. Some of these mods even have original coding in them. But I have the feeling that you're referring to games where every tile and every line of code come from the homebrew community.In [url=http://nesdev.com/bbs/viewtopic.php?p=61358#61358]this post[/url], tokumaru wrote:it's actually a matter of balance... The NES has always had tons of emulators and few homebrew games, and right now this scene needs games more than it needs emulators.
Another example of a tool is a game designed specifically for modding. There's an RPG Maker on the PlayStation, and there's WarioWare DIY on the DS, but that doesn't help with the NES. Or is it my job to make such a game?
Sometimes some of these tools might require specialized emulators, such as a music editor that sends playback commands to an emulated NES.
Older related topics: Homebrew complexity, Where is Super NES homebrew?