I wonder why it wasn't released for the NES
The Empire Strikes Back came out in 1993, which was a bit more than a year before the last licensed NES game and about 2 years after the SNES came out. It just wasn't worth it to make an NES game (hence the SNES version of Return of the Jedi).
and becides, the NES Empire Strikes Back is a pretty worthless game...