The SEGA Dreamcast has always been one of my favorite consoles, despite its untimely demise. In 2008 I decided to begin writing an emulator that could boot and render Dreamcast games on an Xbox 360.
Note that this project only sought to implement those components required to render a game, and not necessarily play it (i.e. limited controller and audio support). After a year however of part-time development, I decided to halt work on this project in favor of other more pressing projects. In its current form it is able to boot a handful of homebrew games and render their attract sequences.
In my original vision, we would support dreamcast games as Xbox Live Marketplace downloads, and the emulator would optionally render the games in HD with multi-sample anti-aliasing.