Why oh why oh why oh why.....

Can anyone shed some light on something that has plagued me for 5 1/2 years? Why won't my kids go to bed? I am trying to do everything right, I read the stories, say the prayers...I even have Lainee include in her prayer for Marlee to go to sleep, and vice versa...I have COVERED my bases. I do the night time ritual, get them water to keep by the bed, go potty, brush teeth, you name it. I've begged, plead, and threatened. I've tried the Nanny 911 technique, my kids laughed at that one. I've been sweet, not sweet, and downright tyrannical. Nothing works on these kiddos. Marlee is especially a problem here. She will get up at 8:00 a.m., go all day long without a break, and I promise you if I would let her she'd stay up until 4:00 in the morning without batting an eye. I would so love to do the bedtime routine, tuck the kids in sweetly and say good-night and shut the door, check on them 5 minutes later to find them sleeping like little angels. In our house, its more the other way around, the kids say good night, shut my door, and 5 minutes later I'm off to la-la land, and heaven only knows what goes on after that. Any suggestions that don't involve the Vulcan neck pinch? Already tried it. Doesn't work.