But, after the crash of Oceanic Flight 815, he started helping and treating everyone once he emerged from the jungle. Also, he removed Ben's tumour with only a few problems (i.e. Jack deliberately cutting a small incision in Ben's kidney sac, Jack revealing that Juliet wanted to let Ben die, and Jack nicking an artery). Well, he was trying to save Kate and Sawyer.
Off-Island, he fixed Sarah's broken back. He also pulled Mrs Arlen and her son out of their burning vehicle. Well, he caused it, but if he didn't, he would have committed suicide and would never have come back to the Island.
That's why Dr Jack Shephard - former spinal surgeon and currently DHARMA workman on the best TV show ever - was picked as one of the "best and brightest in our preferred provider network of the 20 best TV doctors of all time" by AOL Television.
"Stuck in an oversized sandtrap, unflappable Dr. Jack leads the crash survivors of Oceanic Flight 815 on their bizarre island adrift in time and space. And curiously, by becoming lost, Jack finds the leader within. Turns out, he's only truly lost when he returns to civilization -- only the island can give this spinal surgeon some backbone. Go figure."
*Sigh* If only Jack knew what his destiny in 1977 Island already...
Anyway, my other favourite doctors on the list are Dr Miranda Bailey (Grey's Anatomy), Dr Gregory House (House), Dr Doug Ross (the just ended ER), Dr James Kildare (Dr Kildare), Dr Frasier Crane (Frasier), and Dr Douglas "Doogie" Howser (Doogie Howser, MD).
And, oh, my favourite Dr Jack Shephard moment is depicted in the following photo (thanks to Lostpedia):
After Jack and Kate found Charlie hanging from a tree, Jack tried his darnedest to save him. Even if Charlie appeared dead (uh-oh, one of his really close calls with death), he did not let go and pounded Charlie's chest to revive him. It was one of the most harrowing and emotional moments in LOST. And it is one of the reasons I like Dr Jack Shephard.