Motocross Challenge is a racing game somehow similar to Excitebike that was in development by DHG Games for the Nintendo DS. The project originally started as a Gameboy Advance game, but after Motocross Challenge GBA was cancelled, it evolved into a DS game that should have been released in 2009. After some months the official DHG Games website went down without any explanations and the DS version was cancelled too. As the developers shared the GBA version online to let the fans to play it even if it was never published, it could be possible that in the future they will leak the DS version too.
In April 2010 Motocross Challenge was finally released for the iPhone / iPod Touch, so at least it was not lost at all! You can see some videos of the iPhone version in DHGames’ YT Channel or buy Motocross Challenge from the iTunes Store (only $0.99!)