LOST best episodes each season and runner-ups

Season 1: Deus Ex Machina (Runner-up: Raised By One Another)

Locke's first story with his evil dad is sad and emotional, the kidney scene is magnificent, dream visions are crazy awesome, Also, the flashing light from the hatch to the sky, the anger from Locke for island/ Anthony Copper's deceptions is truly touching, of course the falling plane for Boone is really moving too

Season 2: Live Together, Die Alone (Runner-up: The Long Con)

LTDA is my favorite of the series and as a start of Desmond's epic romance story, Penny's letter is perfect. Desmond's faith and his destiny crosses the path of 815ers, how Locke save Desmond's life while Desmond restores Locke's faith. The theme is explored deeply. The first appearance of Charles Widmore is finally becoming more and more important as the story progresses. The purple sky and we first get a glimpse of four-toed statue and the strong white light flashes which suddenly becomes main plot in season 5, a lot more things can be praised here.

Season 3: Through the Looking Glass (Runner-up: Man Behind the Curtain)

My favorite season so far contains the most unforgettable finale in the TV history. The shocking flash-forward, the interaction with Jack and Kate, how desperate Jack looks have changed my perception of Jack totally. The start road for Jack to turn from Man of Science to Man of Faith, and the long-beard Jack is the strongest character transformation in the Lost universe, which leaves season 4's downturn road not satisfying enough compared with this. The suicide attempt, drug addiction, drinking habit are beautifully told and clues are left with care. Clever writing and of course Charlie's heroic death is the highlight of the series, if not the finale only.

Season 4: The Constant (Runner-up: The Shape of Things to Come)

Desmond rules again, the 8-year long love story is compelling. Perfect mix of science fiction and character development. How can a person not emotionally involved after this 40 minutes of sweet stuff? Consciousness travel concept is original and fresh, nose-bleeding and constant finding are on scientific basis at the same time dramatic. Great acting, great story, it leaves the finale Des-Pen reunion into thin paper.

Season 5: 316 (Runner-up: Lafleur)

Jack is getting better every season. The way to open his eyes as opening already acts as a unique trademark for LOST, especially with Jack's pupil.
It starts all over again and new mysteries are introduced for setting up future flashbacks, masterful handling of story and shots. Jack and Ben's dialogues are most memorable, like the resurrection of Jesus story, also like how Eloise tells Jack to take a leap of faith. Jack-Locke interaction is always great in LOST, now including Jack talks with dead Locke. The shoe putting scene is hilarious, yet important for Jack to grow more into Locke's side.