Horrible.
Please don't get me wrong.
The idea is very nice. The graphics are good.
The programation and its physic are very poor and it lacks on movements (link's spin attack is a downward thrust?)
If you want to make a good game make at least an animation of 2 frames for each movement.
Please check the physics. They are VERY poor.
Some advices
-When a player presses the jump key in midair the character sprite goes to the stand position for 0.5 secs and then he jumps (so you can see the 2nd jump)
-When a player falls change the sprite into a jumping one.
-Make the selection screens with less details. Make the logo and above it white words Game A and Game B (those are solo and multi, that's cool cuz it gives a touch of nostalgia) Remove details from the character selection screen. Don't forgive that it's a NES game!
-Remove quality to the midis
-respect the 8x8 sprites and backgrounds order
-Add more vertical acceleration
-If links makes the spin attack in the midair and before it finishes it he touches the ground cancel the spin attack
-NEVER EVER make transparency
-Respect pallets
I think that's all lol
I'm a spriter. If you need anything, just ask me