I watched the first season of LOST, then got bored with it 4-5 episodes into Season 2 and stopped watching.
That's the problem with these series that have one overall continuing premise. They are impossible to sustain. With 22 episodes per season, you have to keep adding story tangents that take you away from the main plot. Eventually, everything gets so complicated that you lose track of what's going on in the basic story.
Some of these series that were cancelled the first year, but allowed to complete their basic storyline (e.g. KIDNAPPED, THE BLACK DONNELLEYS) are among my favorites...if for no other reason that they had a beginning, a middle and an end.