Pitfall I was such a success on the Atari VCS that gamers demanded and got a sequel. Now both games are available on the C64.
Pitfall II takes the basic treasure seeking idea of the game but adds a vertical dimension. And when I say vertical I mean vertical - some of those caves seem to go down forever.
The ultimate aim of the game is to find the lost Raj Diamond hidden somewhere in the caves.
Nasties to overcome include flying bats, poisonous frogs, scorpions, electric eels and - worst of all - the giant condors.
I personally rate Pitfall II higher than the first game. It's more difficult and will consequently take you longer to crack. The game also has a sensible marker system that avoids you having to go right back to the beginning of the game each time you get zapped - you just go back to the last marker.
It's not necessary to have Pitfall I to enjoy the sequel and vice versa.