Be warned -- the music will haunt you forever!
It really wasn't that great of a game but it was memorable for two reasons. Firstly, because you're a guy with balloons on your back flapping your arms, and when you played multiplayer you could pop your friends balloons, which inevitably led to many siblings beating each other up. Secondly, the music somehow engrains itself into your head. I still hum the song from time to time.
As for the actual game -- you were a guy... wearing balloons. I guess you'd call that balloonist? A balloon pilot? Anyhow you tried to avoid hitting lightning bolt things in the air, like a side-scrolling aerial minefield, as well as other things such as weird baddies that wanted you dead. As the level progressed the game got increasingly difficult as most NES games do. That was about it.
It was fun but nothing amazing. The physics of falling and flapping back up -- faster the harder you mashed the button -- were impressive at the time and hadn't been done before as far as I can recall. But in an era where most NES games were very repetiitive, it did very little to break from the mold in that sense.
If you have a penchant for trying out old-school games, it's certainly worth it just to hear the music and get a feeling for what it was like. Though I'm not entirely sure having the music engrained into your head for years to come is such a good thing.