My brother did a pretty decent job of summing things up, at least from his point of view, over here.
Basically, I always liked the show's original premise (I liked the idea of a plane crash onto an island where mysterious things are happening) and I always thought the show had a lot of promise. I guess my biggest gripe is that Lost was a show that seemed to kind of want to swing for the fence- exploring some of life's big existential questions about who we are, why we're here, what our lives mean, and what happens to us when those lives end- but I always just felt a little bit like Lost was pretending to seriously explore those questions while in reality it was just throwing some sort of religious themes and metaphor together and then getting the audience to make the show interesting by projecting things onto it (which can be kind of interesting, but also frustrating if you don't think the show itself has a lot that's especially new or insightful to say). I've always really wanted to like Lost, but in the end, I guess I felt a bit like the show was sort of hustling its audience- playing at exploring deeper questions while, in reality it was just sort of weaving together enough symbols and references to keep its audience intrigued, but without ever really finally delivering on its promise to reach some sort of interesting conclusion.
And I guess that Lost ultimately did reach some sort of conclusions, but were they interesting enough to justify the many years of hide-the-ball storytelling? For most of the Lost viewers (and I guess this is where I part ways with many of Lost's hardcore fans), the plot and characters were enough to keep them engaged. Personally, for me (a fan who kept wandering away from the show, but then returning when I thought they were finally "getting to the point"), the characters were okay, but not all that great. I definitely never found them so interesting that I ever quit asking myself what the heck these people were doing wandering around on a magical island. They just never felt like real people to me.
And I guess the whole mythology of the whole thing bugged me a bit in the end. They created their own sort of pseudo religious mythology and spirituality, but it mostly seemed a lot like various Christian metaphors, with a little bit of new agey, vague, "none of this is specific enough for people to analyze it too closely" gobbledygook thrown in for good measure. In the end, the show seemed to indicate the existence of an afterlife where we get to be with the people who were the most important to us, and then we go into a great white light. We all go into the light together (even the people who haven't died yet) because, although we don't all die together at the same time, we all eventually do die, and the place where we wait to meet up with each other exists outside of time. And, of course, the characters all met up in a church in order to complete their journey, but, predictably (at least by Hollywood standards), the church had stained glass windows which incorporated religious symbols that were not simply Christian, but taken from a variety of different religious traditions- and frankly, I woulda had a little more respect if they had just nailed the ending down as being Christian- we already had Jack playing a pretty clear Jesus figure throughout the final episode with the self sacrifice, leading a group of followers to a place where he saves the world by stopping evil, dying with a wound in his side and being reunited with his father in the afterlife, and the whole communion with water thing).
There's always been this school of thought that the whole island was heaven or hell or purgatory, but in the Lost tradition of trying to have your cake and eat it too, the writers ultimately seemed like they created a separate dimension just so that they could have a clear cut purgatory ending, but also have an ending with a final battle between good and evil for control of the island and in which Jack could become the savior of humanity.
Anyway, Lost ultimately provided some answers, I guess, but I'm just not sure they were answers that I found very interesting.
I know that my saying this will tick a lot of people off, but I actually found the Battlestar Galactica finale (which a lot of people hated) a lot more interesting than the Lost finale, and I would hold the BSG finale up as a demonstration of why I found that show, overall, to be more satisfying.
A lot of people disliked the BSG finale because it had some kind of weird ideas in it, and to many people it seemed like a departure from the rest of the show. But the ideas in the Battlestar Galactica finale were actually ideas which had been present throughout the entire series and which only came to fruition in the finale and the last few episodes. Battlestar Galactica ended with a plotline in which it became clear that the humans and the cylons had been existing in a repeating cycle- a cycle which had been going on for millenia and which would probably be repeated again (although at the end of the series there seemed to be some hope that the cycle might have finally been broken). This idea seemed a little strange to much of the BSG audience, but the concepts were actually taken from Hindu metaphysics and cosmology, a belief system which predates Christianity and which is probably just about the oldest of the world's major religions. In addition, the Hindu themes, which didn't really crystalize until the latter part of the series, were actually contained throughout the run of the entire show, with the lyrics from the show's haunting theme song (or at least the lyrics from the first few seasons) taken famous Hindu mantra, the Gayatri Mantra, which is derived from the Hindu holy work, the Rig Veda. Throughout the series, a theme arose in which characters (and even the voiceover at the beginning of the show) pondered the possibility that "this has all happened before and will all happen again".
So I think that BSG actually had a pretty strong ending, but a lot of people didn't really give it the credit that it deserved because a lot of people just didn't really "get" the incorporation of Hindu theology into a western sci-fi show. Anyway, I'm not here to say that BSG was the be all end all of television, but I will say that it delivered something unique and sort of profound in its final few episodes, and I remember thinking about that finale a bit in the days and weeks after it aired. It was kind of cool to have a show make me think about things in new and interesting ways- to examine ways of thinking that I just hadn't put much thought into since I studied philosophy and Asian religions during undergrad.
With Lost, on the other hand, I just felt like they just touched on a lot of things in order to make the show seem sort of ambiguous and open to interpretation before ultimately falling back on some pretty thick (but pretty run of the mill) Christian metaphor. I suppose that at some point during the series they had realized that their audience was too clever to be kept guessing with direct metaphor, so they sort of came up with a bit of their own mythology (heavily reminiscent of a lot of Christian stories, but not directly corresponding to them) in order to keep the viewers intrigued, but in the end, the story still boiled down to Jack as Jesus. The rest of the show ended up mostly being red herrings looking at themselves through smoke at mirrors that led to rabbit trails.
And I don't want to be too hard on a show for failing to dazzle me with its theology and philosophy (since most shows don't even include those themes in the first place), but at the same time, Lost has never been afraid to tout itself on its ability to explore big questions, so I don't think I'm being too unfair when I take a hard look at what some of the answers that it ultimately presented.
Oh well, at least it made me think and question and debate during the run of the show, so that's a pretty good thing, but I think that in the end, Lost will be remembered far more because of the reaction that the audience had to the show (with the massive internet discussion and buzz and the extensive hyperanalysis) than because of the show itself. But maybe that's okay.