Haha, I remember when I saw a custom made Rom of Super Smash Bros for the Super Nintendo. It was called "Kart Fighter", now I didn't know it was custom made, so I downloaded it, and oh did I hate it!
Although that kind of talk probably isn't allowed on this forum (feel free to edit it out).
Anyway, Super Smash Bros would actually be alright to see on the Nintendo DS, obviously it woudn't beat Brawl but it would be a nice game to carry around in your pocket and play anytime.