Many posts and theories on here seem to argue over whether Jack or John is "right", and what's the correct approach to living on the island. The show sets up this conflict very early on with "Man of Science, Man of Faith." A question in the back of my mind during my most recent rewatch has been "which of them is actually right?"
After my first viewing I assumed that the faith path was "right", and that we're seeing Jack arc from being a rationalist unbeliever into being a believer guided by Locke and the island, and then he'll become a good leader. But the more I look at Locke, the less I think that his brand of faith is the right way to go.
Locke is arguably delusional and crazy. He has a deep seated need to feel special, and throws himself into things without considering the ramifications if they make him feel special. Again and again he is shown to be extremely gullible. Cooper conned him out of his kidney in part because he was obsessed with being special to his father. Locke also conned himself into believing in a fake relationship with a phone sex operator who he called Helen. He also liked fantasy in other benign ways, for example, being called Colonel when he played risk. This is all before he even got to the island.
Take a gullible person like this who has a huge chip on their shoulder, then drop them on an island and cure their paralysis. We end up with someone who is certain he's divinely blessed and is itching to figure out what their mission is. The audience wants to buy into Locke because that's what we're used to doing as an audience, but there were many signs from early on that imply that he's actually just an insecure man who is grasping for signs of approval and specialness. He justified anything good or bad he did as being because the island needed him to do it. Locke claimed to commune with the island, but we never saw what he saw. He found the hatch because he was meant to, and he was also meant to open it. Boone died because "the island wanted it". He was in divine awe of the hatch when Desmond flipped the light switch on to see who was banging on it.
This makes Locke the perfect candidate to be manipulated. He indiscriminately believes everything that seems super-normal. He went along with anything his visions told him to. He went along with everything Walt told him to, including knifing Naomi. He appears to have unwittingly manipulated himself into a leadership position in the Others that only exists because of things he told Richard in the past. We have no idea what John did that was was influenced by MIB, and what was influenced by Jacob. His fatal flaw was that he had absolute faith in everything.
In some ways, Jack is almost exactly the same as Locke. When John thinks he has a mission to accomplish, Jack looks for things that are broken and tries to fix them. Jack is completely driven to fix things. His flaw is that he picks whatever's right in front of him and immediately tries to fix it, even if evidence suggests that it isn't broken or simply isn't meant to be. Like Locke, this is reflected in Jack's flashbacks, particularly anything having to do with Sarah.
Jack's flaw isn't that he doesn't have faith, it's that he doesn't acknowledge that there's something special about the island and that he and the other survivors do seem to be there for some reason. Nearing the end of season 5 he seems to evolve somewhat. He doesn't fix Ben because he doesn't think there's a reason to, which may be the first time in Jack's life where he didn't go try and fix something. After Daniel gets shot, he takes on his task to detonate the nuke. But his motive is still flawed. He says that his reason for carrying out the plan is that he wants to erase all the horrible things that happened to the 815ers so that they land safely at LAX. In a twisted way, the nuke is actually the latest of his attempts to do what he's been trying to do for the entire show - get all the survivors safely off the island. Jack has obviously grown some, but is still trying variations on the same old tired routine.
Upon inspection, neither Jack nor John look really great. What if the answer is that neither of them is right? There have been hints that there's a better middle ground. MIB's major complaint to Jacob is that newcomers fight, corrupt, and destroy. In the same episode we see Rose and Bernard expound on how the 815ers are always running around fighting and blowing things up. They ask Juliet to stay for tea rather than go tromping off. In fact, Rose was also against Locke - when the group splits in The Beginning of the End she says "I'm not going anywhere with that man." in reference to him. The Rose and Bernard of the 70's seem to be showing the audience what the voice of reason is.
So, if Jack and John aren't right who is? I'd say it has to be Sawyer.
I think Sawyer may become the show's real hero and leader. He has grown immensely over the course of the show. He learned to have real personal relationships. He clearly cares for many of the characters. He is also very protective of his people, but not in an unhealthily obsessive way like Jack is. At times he has been completely selfless in his protective acts, such as when he pulled a gun on Locke to keep Hurley from having to go to the cabin if Hurley didn't want to.
Sawyer is also the only main character who seems to actively want to settle down on the island and make a life for himself there. Locke doesn't even really seem to want to settle down, he just wants to find his destiny. Sawyer's settling didn't start out in the most appealing of ways - he hoarded items and declared that it was Lord of the Flies time. But as more people looked up to him and he grew to care for people, that transformed into a much healthier form of settling. One of my favorite episodes, Left Behind, is a turning point for him - Hurley cons him into being nice to people and ever since then we see Sawyer in a much more benevolent role whenever he's in charge. A little after that he tried to get Kate to settle in with him on the beach, but then the plot rollercoastered. In Eggtown we see him again trying to settle down: "Hello ladies - coffee smells good!" He makes a heartfelt appeal to Kate that they can make a life in the barracks. Then after the time jumps he almost singlehandedly orchestrates a good life for his group in DHARMA. He and Juliet seemed happy, and he actively tried to protect their life together. His main argument against detonating Jughead was that Jack was ruining the good lives that they had built up for themselves.
It's my hope that in season 6 we'll see that neither Jack nor Locke really is "right". Jack may end up as the hero who prevents some form of catastrophe, but I bet Sawyer is going to be the one left at the end who can actually lead the remaining survivors in a peaceful new existence.