1) I am not one for hyperbole, but LOST is the best show in the history of television.
2) If you aren't into LOST, or haven't had a chance to see the last episode, then stop reading now (but I strongly suggest you do yourself a favor and watch this series).
3) I don't claim to have the answers, but I do have some thoughts about how it all ended...
So, from the very beginning of the show, many people have believed that the survivors of Oceanic Flight 815 were not, in fact, survivors - but rather, they died and were in a hell-like state without knowing this. It seemed, in the beginning seasons of the show, that the survivors (or at least the main characters) had some pretty significant misdeeds they needed to pay for. However, as things developed, we started to feel more like rather than paying for their sins, they needed to go through a redemptive process and become better people.
Sometime during season 4, I started to figure out that although the island was in fact a place on earth, it was dimensionally slippery. What I mean by that is the island is not completely a part of the physical world as we experience it. The island exists in a dimension that can be reached from the earth (if you know how to get there - or by some circumstantial accident), but the island also belongs to a spiritual dimension. So, the nature of the island is a bit slippery. Later on, we learn that the island is more of a gateway between the physical earth and some spiritual realm, with the island acting as a "cork," keeping the evil of this other realm out.
So, in short, we have flawed people living on an island that is in some in-between spiritual dimension. And if that wasn't hard enough...
What made this show very difficult for people (I think) is the shifting of exactly who the antagonist(s) is/are. Who are the bad guys? It seemed that almost every season the "bad guy" wasn't much of a bad guy anymore, but rather someone who just understood the nature of things better and therefore behaved in a way that scared those who didn't fully understand what was going on. So, good guys became bad guys; bad guys became good guys; bad guys became good, then bad, then good, then bad, and finally good (Ben).
Up until the last couple episodes it was still pretty unclear who the really bad guys were. But I think that is one of the major points of the show. How many people or situations do we know that are 100% good or totally bad in their behavior and motivation? What we knew was that we loved the characters and we wanted them to be happy (redeemed). What the entire show really boiled down was to answer the character questions: Would these survivors become better people? Would they make the right choices? More specifically, the show is about Jack Shepard. Will he make the right choice(s) and make up for his past issues. Will he become the person he is supposed to become?
All along, the island was a creative setting (with it's slippery time, realm, and location) for a long, comprehensive look at human-kind and the power of personal redemption. Ultimately, Jack overcame his tendency to be a skeptic, combining his new-found faith with his leadership qualities and saving his people, the island, and (I guess) all of us (though exactly how the rest of the world was in danger clearly was left to your interpretation).
My theory for what was revealed in the last episode: The flash-sideways sequence was (yet another) spiritual realm where everybody went to after they died (again, Jack's inclination was to not accept this reality). Some died before Jack (like Charlie), and some "much later" (like Kate, Sawyer, and Claire). However, as they all had profound life-changing experiences on this island together, they were connected spiritually and it was arranged (by Hurley and Ben is my guess) that they would be brought together as they "move on" into a new existence (the after-life). The idea is that we move on to the after-life with the people who matter the most to us - this would include people who we had such life-altering experiences with. Obviously this all requires some suspension of disbelief, but I think it is a beautiful ending to a profound show.
As I conclude, let me give the argument for why I love this show so much. LOST is full of allusions: religious (heaven, hell, in-between purgatory-like state), philosophical (names like Locke and Hume), literary (in almost every episode someone is reading a book having to do with a theme of what was happening in the show at that time - for example, as we start realizing that the island is one big housing of electro-magnetic energy, we see references to Stephen Hawkings books), and all with a heavy dose of scientific theory and speculation. By the way, my examples in the parenthesis are just scraping the depth of the allusions... you literally can not keep up with all the references in the show. And if this weren't enough... PUT ALL THESE THINGS ON AN UNCHARTED ISLAND WITH PEOPLE TRYING TO SURVIVE AND I AM SOLD!!! And then they went ahead and EXCEEDED my expectations over and over.
Ok, really, as I end here I want to mention my new favorite thing about LOST. Well, I realize that it has always been one of my favorite aspects of the show, but it was more sub-conscious. I recently realized how in love I am with Michael Giachinno's music. The score for LOST is superb. If you get a chance, listen to just the musical elements of the show, and you can feel the emotion without any images. I am his new biggest fan.
If you get a chance, check out youtube and check out the video "I'll Never Be Lost Again." Another first for me -- I've never gotten emotional over a hip-hop song before.
