Fire 'N Ice, A.K.A. Solomon's Key 2, is probably on my top-5 NES games.
Fantastic gameplay for anyone who likes puzzle games. The game is easy to pick up and play in short bouts, and boasts 90 levels altogether.
You play as this little wizard guy and you have to put out all the fires in the level. You can create and destroy ice blocks with your wand, push ice blocks, and climb on to them. Later levels introduce more complex gimmicks like tubes and black ice which you can't destroy.
Aside from the very smooth gameplay, Fire 'N Ice has a really polished presentation. This game came out in 1992 in Japan, 2 years after the SNES was already released, so it's not surprising that the sound and visuals are top-notch.
Check it out if you like Sudoku, Picross, Tetris, Panel de Pon, or Dr Mario.