I can totally relate! My 3.5yo son always gave me hard time when it came to sleep ever since he was a newborn. The crib is what was saving my life, but ever since he's been out of it before 2, I strugged.
We always co-slept from the start. It's not a bad habit - if it makes your life easier, then do it! Read a lot on pros of co-sleeping, and you might change your mind.
My son doesn't take naps anymore, and if he does, he'll be up until 11pm-midnight. So he's tired by 6:30pm, which is his bedtime... except I take him for a car ride. I've been doing this for over a year now. DH and I simply stopped fighting him.
Nothing worked. Sticker chart, Supernanny, bedtime routine, tiring him out, "locking" him in his room (I stood outside the door to hold the door shut). He would scream and bang his head on the door/wall when we did that. He would just get too worked up, so we gave up this fight. What used to work for a while is laying down and watching TV on the couch in the dark. But as the day started getting longer, it stopped working.
Previous posters mentioned chamomile tea and melatonin. I've tried the tea too. I think melatonin will be useless because he's tired - he just hates going to sleep.
I think some kids can't shut off their minds to go to sleep, or they might miss something fun and important. You can't really fight it. They'll be the same way when they become adults (I'm sure my son got it from my hubby).
Good luck, and LMK if you find a solution!