Originally, I was really, really over thinking it. I won't even get into what my original theories were. But trust me when I say, they were deep.
But here's my final (or should I say, Finale) theory. (Come on, people! You could at least crack a smile at my corny jokes....)
Season 6 flipped between life on the island combined with the flashes to a life that never really was. A false reality. (In the excerpts of the dvd we watched, they called it the "Sideways" life.) It was a great life, but still not perfect. It was a life that they created for themselves. A life surrounded by the people that they bonded with during their time on the island.
And it was a happy life, for most. But still plagued with problems. Kate was still running from the law, John Locke was still crippled, Sun and Jin were still trying to get away from her dad.... Even in a false reality, no life was perfect.
My assumption (after much discussion and the all night dreams...) is that the sideways life was a type of purgatory. Life between real life and death.
The life on the island was real. Bizarre. Strange. Crazy. But real, nonetheless.
That being said, they would have actually lived through the initial plane crash. They would have "flashed" before the second plane crash and they would have actually died off one by one on or off the island.*
But in order to meet their final eternal destiny, they had to find one another in the sideways life. They had to connect to their real lives and stop clinging to the life they thought they had in order to find something even more lasting.
And I think it's beautiful.
And as long as you take it at face value.
The show was mysterious, intriguing and amazing.
It was happy and sad, ya know?
And personally, I think the Finale reflected all of that to perfection.
Let's just say I have way more closure about the finale of LOST than I do about the finale of Seinfeld.**
Now, please, excuse me while I go Google what other people are saying about the Finale.
*Again, this was not my original assumption. I didn't think this until I remembered that handful of people who actually got off the island. Not to mention Kate's words to Jack outside of the church. I've missed you so much. Meaning Kate, once on the plane, did actually make it off the island and live the rest of her life without Jack.
**I am still scarred from that one!