I also don't get the Jack hate/Locke love thing that prevails....Locke became an extremely one dimensional character towards the end of season one. Then about half way through season two he swapped to a faithless wreck who whined and did some really stupid things for a couple of eps, then swapped back again, then back again, and just nothing new for ages...And as Solius says, did some fecking idiotic things in the name of his "faith. His flashbacks got pointless and repetitive as well (the one with the hitchhiker? that was quite pointless) as we all were just waiting for the one where they showed us how he was crippled for ages.
Terry O'Quinn was so good though that no one seemed to mind his character was a massive cock end at times. This Locke is easily my favorite since season one...he's better now.
Jack I've always liked, and Fox has always put in good performances when called upon, but again he's suffered from a series of similar archs....but that's just a casualty of the show not having an end date for so long. Sawyer has benefited from starting out a relative villan and thus having the most profound arch, and the most to work with. Ben similarly, because it just makes them more interesting. Both actors have knocked it out the park when called upon really.
Desmond would've floundered as a character if he'd been as prominent as Jack or Locke I think, even though I agree he's a complete lege. It helps he's been a periphery character with a big role in the mythology.
All in all, I generally root for Jack, and I don't get the hate either....Kate on the other hand, has become a completely useless character who hasn't changed since day one.