I always thought Jack behaved in a self rightous manner. IMO he always thinks his way is the right way. I mean don't get me wrong I like Jack, but I think back to what Sarah said. Jack needs something to fix and once he does that thing or person is not that important to him anymore. He is a good person but his motivations for helping people are often (if not always) selfish ones.
And as for a more general reply to you opening post. This show like all shows is going to change and evolve. That is just the way it is. The characters change too. During the run of the show my like and dislike of certain things and characters goes back and forth. But the overall grand story that is being told on Lost is something I really like and I may not like how the series ends or an episode or two along the way but I want to complete the ride.
