I haven't read the other replies yet, so bear with me if this is repetative.;)
I have had the same issues with ALL of my children around the time they figured out how to get out of their cribs and/or were moved to a toddler bed.
My husband and I tried everything!! I realized they wanted to participate in whatever dh and I were up to, and tended to fall asleep while sitting with us on the couch. We went through a night routine as usual, and instead of us both getting anxious and geared up for a pending battle, I have told them it is quiet time and as long as there is silence and everyone sits nicely, they can stay up with us. So the little kids who have a little more trouble sitting still cuddle on dh and my laps. I also use it as a good training opportunity for getting them used to sitting still at places like dr.s offices, etc. They have since stopped the bedtime resistance. They don't feel like I am shoving them off to bed and hating every second of the battle with them. I think the sudden adversarial (me against the kid) nature that can take over at bedtime and the frustrated ' you will obey or else!' and the kids ' durned if I will!' attitude and equal bullheadedness back and forth escalation can throw a kid into uncertainty about where they stand with a parent, and why the parent doesn't want to be with them. At that age they just don't understand. After a year of this EVERY night I realized how terrifically unhappy(usually in tears) and wired everyone was by the time one of gave up us out of sheer exhaustion. My oldest is five- six in two months, and he goes to bed pretty much on his own now when the 'relaxing' time is over.
I try to keep it welcoming, relaxed for everybody, make sure needs are met, ( thirsty, hungry, attention needs, cuddles, cheerful attitude, low key play, tickles, kisses and ALL the kids blankies and pillows around, OF COURSE:)
We put everyone to bed around 10ish. The atmosphere is ten times better, and when a kid doesn't want to go to bed, their is usually a need for some one on one or they had a bad day and need extra cuddles, etc. etc.
Hope this helps- I don't stick to a system of parenting- I try to do what works for my children and our family.:)