I have to say, while the DS and GBA homebrew scenes were vibrant (and are still not dead), I keep hoping for the release of the various SNES flashcarts to promote homebrew there. So far, I'm disappointed though. Some things (like blargg's Eine Kleine Nachtmusik audio demo and N-Warp Daisakusen) are neat, but strictly as tech demos. I keep hoping some decent games will be made eventually.

NES has some good homebrew though (D-pad Hero, Battle Kid), and the Genesis seems to have some looming as well (Pier Solar, if it ever gets released).