To start out with, I think the reason that I was not completely satisfied with Lost's ending can in part be explained by comparing it to the Ashes to Ashes finale.
They both ended incredibly similarly, and I've have to say, Lost's finale made me appreciate Ashes to Ashes more. When Shaz, Chris and Ray realized that they were dead, I really felt for them. I mourned with them. But when the characters on Lost realized they were dead, it was kind of just this weird vacant smile that was a bit creepy. And it was way too easy.
And then when Shaz, Ray, Chris and Alex moved on to the Railway Arms, I felt a nice sense of completion because their lives were over and they were going to start their new afterlives. Their lives in the real world were over (and had been for sometime). They had resolved their issues in Gene's World and could move on with nothing holding them back. It wasn't easy, but it did feel right and complete.
But on Lost, I just didn't get that. Kate, Sawyer, Hurley, Miles, etc were still alive from the viewer's POV. I mean, I know that there is no time in the limbo, but really from the audience's POV, they had all just taken off on the plane or were going to stay on the island as the new Jacob. We don't get to see their lives, but it is entirely possible that they live into their seventies. So maybe they meet other people and fall in love with other people. Maybe Sawyer and Kate get together. Their lives are unfinished. But since they were in the church with all of those who had died, it feels like their entire lives were reduced to time spent on the Island. It doesn't matter what happened after Jack died because the limbo was all about the Island.
The ending would have worked much better for me if only those who had already died when Jack died were in the church. Christian could have just said that the others will join them when their time on Earth is over. But then we couldn't have had a ~dramatic reunion between Sawyer and Juliet or Jack and Kate.
Instead we just get that apparently their entire lives amounted to nothing after they left the Island which takes away all the joy of the Ajira plane taking off. It creates this "yay! They got off the Island!" but then "oh wait. LULZ. It doesn't matter because they did nothing of worth afterward. They didn't fall in love with anyone else or build relationships with other people. They were never able to move on." So you kind of get this really depressing ending for characters that you should be excited about surviving.
For me, the ending would have worked so much better if there WAS a sense of time in the limbo/purgatory. Those who were still alive in the real world wouldn't have flashed yet. I think the ones who were dead could have flashed on them, but then Desmond (as the guide figure) would tell them that Kate or Sawyer or whoever wasn't ready to move on yet, but they would join them soon. It just rang so false to me. I hated that they essentially took away any possible awesomeness and life that Sawyer, Kate, Hurley, Claire etc might have had after getting off the island to make their afterlife (or limbo at least- maybe after they go into the light Claire is like "peace out, suckers! I met an awesome guy when I got home!" or Kate and Sawyer are like "remember how we got married and had awesome and beautiful kids together?") about ONLY what had happened on the Island. It makes their escape seem so purposeless.
But the way that they ended the storyline in the real world was very open ended. Honestly though, I don't think that any of the characters would really be able to establish relationships with other people because no one would believe them, or even if they believed them, they wouldn't really be able to understand how the island changed them. Therefore the only two solutions left are: the Losties left alive end up together or are very alone.
Claire, I think, is alone. She is a bit too crazy. I don't think she'd ever be normal enough again to have a relationship. But I do think that she gets to be reuinted with her mom and she and Aaron (and Kate and possibly Sawyer too) are able to carve out a life for themselves
Kate? I think she got to continue to help raise Aaron with Claire. Also, Kate is an A+++ baby stealer. So I want her to steal Ji Yeon so that Daddy Paik can't get to her. And I do think that she ended up with Sawyer in the real world. I think that Sawyer and Kate still shared something of a connection. Sure, I think it will take time for them to get over the loss of Jack and Juliet, but I do think they will end up together off island. They have a bond and attraction and they will never be able to find anyone else who will really be able to understand them or what they went through.
I think that Sawyer, as I said, will end up with Kate. But I also think that he will meet up with Cassidy and get to be a real father to Clementine (facilitated by Kate).
I don't know what will happen to Miles, Richard and Lepedis, but I like to imagine that it involves some sort of awesome crime solving and fighting agency.
Hurley and Ben find a way to get Desmond home to Penny and they (and Charlie) live happily ever after while Hurley and Ben continue to be awesome and besties on the Island until Hurley decides that it is time to pass the torch.
So you see, these people have the chance at maybe having something of a good life. And I like to believe that they live to be old people. I want them to have found happiness off the Island. But I don't think the finale left that possibility open to me. What the finale told me is that the only part of their lives that mattered was the Island. Anyone they might have loved who wasn't on the Island didn't get to go into the afterlife with them. So that moment of joy Jack had when he saw the Ajira flight take off? MEANINGLESS because apparently their lives were miserable and they lived in some sort of stasis until they died. Why bother? They might as well have just not left the island and thrown themselves into the ocean.
It was also a little bit frustrating to me that the two relationships that really got the least exploration on the show and generally happened off camera ended up being the TRUE LOVE relationships. It just doesn't have as much emotional impact. Sure we saw a lot of build up to the Jack/Kate relationship. But of them actually together? We pretty much saw a couple of happy scenes and then a horrible relationship and breakup. How are we supposed to be happy that they're going to be together forever?
And Sawyer and Juliet? They barely said 5 words to each other before season 5. Then time flashes and we enter into them mid relationship. It just wasn't believable on an emotional level. I had no connection to them. And then we got three scene of them happy together. And then a tragic death scene. I'm sorry. I don't care about them. I have no time or emotions invested into their relationship, so I'm not exactly like "yay! Together forever!".
Anyway, other than that, I did enjoy the finale for the most part. The stuff with the pool of light was great. And you should have heard me going "NOOOOOOOOOOOOOOOOOOOOOOO!" when I thought Desmond might be dead. haha. I loved the scene where Jack killed the Man in Black. I like Ben's redemption. I LOVED what happened with Jack. I have gone through extreme Jack hating periods, but tonight, I loved him. And I was genuinely moved as he died with Vincint next to him.
There was a lot of little stuff that I liked. But the ending really just left me unsatisfied.