I'm going to go out on a limb here, but I think I view Lost in a very different light than most of the posters in this thread.
Sure, the first few episodes way back in Season One had me hooked with the secrets of the island and all the different mysteries the survivors encountered. I was always on the edge of my seat, looking for new clues that would somehow help to solve the riddles and help the survivors make their way back home.
But somewhere in the middle of Season One, I realized why the show appealed to me, and it wasn't because of the all the unanswered questions or riddles or mysteries that surround the characters. Rather, I watched the show because of the characters, not because of the mysteries of the island. I realized that the more I found out about the past of the characters, and the more the personalities were fleshed out after the Pilot, the more connected I felt to the show.
The characters in the show, although made up and most running from suspect pasts, nevertheless endured struggles and challenges that I think we as viewers can relate to, if not completely, at least to a certain extent. I'm sure every one of us, has, at some point been betrayed, or hurt, or has felt any one of the other feelings that the characters in Lost had to experience before their arrival on the island. Sure, the character histories are just as made-up as the storyline of the survivors on the island, but the fact that the pasts of the characters are so believable, makes it easy to connect and relate to a majority of the characters.
I guess the point I'm trying to make here is that the show is more than just finding the meaning of the numbers, or figuring out why the black smoke kills (or doesn't kill, as the case may be.) It's about us. Us as people. Us as individuals that go through life experiencing events that will later shape how we deal with other events and circumstances in our life. Why else would the majority of these episodes feature a flashback that runs parallel to the main story on the island? Certainly not character development, as the main characters were adequately portrayed during Season One. The character flashbacks serve to show us how our past, and how we deal with it, will affect the decisions we make regarding ourselves and others. In the end, these decisions will ultimately affect the relationships between our friends, allies, and foes.
I don't see Lost as a big mystery puzzle, with hidden answers, cryptic challenges, and impenetrable secrets. Rather, I see it as a reflection of the relationships we build between individuals and how our past, will ultimately and always, influence us, long after we think those chapters of our lives have been closed.
But that's just me.
How's that for seeing the forest for the trees?
(Or maybe I'm just a sucker for good character development and excellent acting from incredibly good-looking people.)
(OK, so the riddles and unanswered questions are kinda cool, especially with how everyone is connected with everyone else, but still...)