I liked Clyde's Adventure a shareware PC 2d side scroller. There was just something about the way you could gradually climb a long way up, come to the end of a platform without any obvious place to go next, take a giant leap, fall and fall and fall and fall for a looooong time, land on the very tip of an ice platform, slide off into a pool of lava before you could react, SCREAM! (yes, Clyde actually screamed), and blink out of existence.
I also loved the first 2 Fallouts.