Would you like a poster of this with no watermarks? Mail me, we'll talk.

I just started playing this game on the NES emulator last week. It's really great; it's a shame it was never as popular as Mario, Metroid or Zelda.
The controls are done just right: very responsive, and the jump physics aren't too floaty. The level of challenge is perfect as well: not too easy, and a constant onslaught of ennemies keeps you on your toes and prevents the game from ever being boring. The password system makes the semi-high difficulty well balanced since you can start over at the beginning of the level in which you died.

Also, the music is really catchy, and the game looks great; except maybe the blue of the sky in level 2 which is a bit saturated (but you get used to it).

I recommend this game to fans of platformers and side scrolling shooters with a well balanced level of challenge. The action is really relentless in this game which is why it's so good in my opinion. So if you like that kind of stuff you should definitely play it.
Hopefully a sequel or remake will be made on the Wii some time in the near future.