One of the things I enjoy about LOST, in addition to the wonderfully creative story telling, is that it draws on ultimate themes that are true about humanity. Deep truths that God has written on our hearts. It's what Francis Schaeffer called "the back of the book." There are things that are true of all people.
Desire for restoration and redemption. Good, evil. Need and seeking purpose.
Man's tragic brokenness, need for healing, and magnificent dignity.
Love and community. Final fulfillment and reconciliation. These
themes were all through the six seasons of LOST and they were
beautifully portrayed in the finale.
Of course, the theology is wrong. Their solution to man's dilemma is grievously wrong. Non-Christians aren't going to get the theology right; they're only dealing with general revelation. But as God's creatures, they understand some of the general, ultimate things that are true about all of us, told an amazing story, and I think that's why LOST captured the audience it did.
Our characters got what all of humanity desires. They found their purpose, reconciliation, and (most of them) redemption. We all die sometime, and this reunion is some time in the future after the survivors have lived out their lives, which we can fill in with our imaginations. It still gives us something to think about. Jack finally fulfilled his purpose, found peace, and was our hero. It's going too far to say he was a Messiah figure, but his death represents the greatest kind of love - to sacrifice for others. And of course, Michael Giacchiano's evocative music helped tell the story of the struggle in life and death the characters faced. I really think a significant portion of LOST's success and ability to connect with viewers to tell the stories is due to his music.
The universalism at the end was pedantic. The solution to these ultimate themes is obviously wrong. A lot of questions weren't answered, but there was resolution.
LOST tapped into fundamental truths of humanity and told an epic story of struggle along those themes. And it sought to give the characters what all humanity desires in the end, a happy ending. That is excellent story telling. The program told us true things about humanity and our condition. It's our job and privilege as ambassadors for Christ to tap into those deep feelings and intuitions people have and point them to the answer and ultimate object of their desires, the Way, the Truth, and the Life. No one comes without Him.
Here's a really excellent post by Lael Arrington about three alternate endings to LOST.