Earthbound
If you don't know what that is, click on it. NOW.
Definitely. I'd kill a man for a plush Mr. Saturn. Well, maybe maim. Alright. Perhaps I'd make unflattering remarks and backhanded compliments. In any event it'd be awesome to have one.
Anyway...
NESBasewars: Baseball with fighting robots that explode...in space!
Blue Marlin: Mmmm, fishing.
Dragon Warrior 2-4: I don't know that these are under the radar but they are pretty hard to find from what I hear.
Geurilla War: Shoot first! And second! In fact, keep shooting! Similar to Ikari warriors but it doesn't suck.
Kabuki Quantum Fighter: Sort of a sci-fi Ninja Gaiden. One of the best action games for the NES in my opinion.
Kickle Cubicle: A fun little action puzzle game. Freeze enemies solid and use them to build a way towards the exit.
Low G Man: Leap super high! Kill robots with a spear!
M.U.L.E: Space colonization strategy game. Can you catch the Mountain Wampus? (Hint: It's not a venereal disease)
Metal Storm: Action game in which you can flip back and forth between the floor and cieling. Pretty nifty.
Silkworm: Play as a jeep or helicoptor, or both in two the two player mode of this shoot-em-up.
Super Dodge Ball: What dodgeball would be like if we could turn the ball into a freakin' laser through sheer will power. Play this now.
Uninvited: A point and click horror story. Actually pretty creepy despite the old school graphics and sound.