Its a shame that no one mentioned Trolls on treasure island - that game is just so much fun its rediculous...
River city Ransom is definitly on the top of the list along with Super Dodge Ball
Battle toads is a lot of fun but its almost unplayable with 2 people because you cant get past level 3 - unless you cheat
I had a lot of fun with the 3 stooges back in the day - Mini games rule!
I really liked the 2 player ability in little ninja bros.
Mario Bros is awesome 2 player
Archon is just great but I play it all the time and its hard to find good competition!
Danny Sulivan's Indy Heat is hands down my favorite Racing game on the NES 1 player is good - 2 player is great - 4 player is unbelieveable!
Qix gets a nod but its nothing special because its the NES version
The rest are already on the list and covered!