Not to seem like i'm disagreeing with everything DR MattH says, but i actually can see why people would say LOST and HEROES are similar.
I mean i would definitely recommend either to someone who only watched one of these. Plus most people i know who watch one, actually watch both.
I"m not saying the stories are the same. But they are both quite complex. And to me are the same style of show.
Btw, i cannot wait till LOST starts! It's one of my favorite shows (as is HEROES).
Their dissimilarites are in the story arcs.
Their similarities are in the supernatural events that impact/affect the characters, and the variety of characters, each of whom is unique.
In "Lost", the island is a mystical/magical/incomprehensible place where they must survive, and the world outside seems "lost".
In "Heroes", the world is changing and humans are evolving, several of whom are developing mystical/magical/incomprehensible powers and must hide from the world in order to survive.
In "Lost", the major characters all have different experiences with whatever power controls the island. In "Heroes", the major characters all have different powers with which they must unite and save the world.
In "Lost", many of the major characters want to return to a normal life while a few wish to remain and experience the unexplainable. In "Heroes", some of the major characters want to return to a normal life while others wish to use their powers to make the world a better place for everyone.
There are no other shows like them.