Definitely not first, but easily one of the best "traditional" Super Mario Bros. 1 hacks around! The graphics are changed a little, but the levels themselves present twenty all-new challenges! The first quest shouldn't be too too difficult, but the second quest was made specially different from the normal mode for an extra hair-pulling challenge!
Super Mario Bros. (World).nes
CRC32: 3337EC46
MD5: 811B027EAF99C2DEF7B933C5208636DE
SHA-1: EA343F4E445A9050D4B4FBAC2C77D0693B1D0922
SHA-256: F61548FDF1670CFFEFCC4F0B7BDCDD9EABA0C226E3B74F8666071496988248DE