Super Mario World (NES) was going to have all the levels, but at some point the development team ran out of time. Incomplete forms of the levels can be played if you hack it. This site can tell you all about it:

http://www.bripro.com/low/obscure/in...p?page=hko_smw

This guy also does a lot of really cool stuff. He's porting the entire city of Portland from GTA III to the NES. Link here:

http://www.grandtheftendo.com/