You poor thing, can truly sympathise. Have a 2.5 DS and on day 4 of getting him to bed, so I can have my evening back. (Just back from holiday, and on a mission!)
He has just stopped having a day time sleep and I spend all day wearing him out so that he really is tired. After bath time he has milk, read him 2 stories and then say goodnight, and put him in bed. Leave night light on and the door ajar.
First night he must have got up about 50 times, I just kept putting him back and not saying anything. He was REALLY stroppy and complained big time.
After about an hour I told him if he got up again, I'd shut the door, and then had to follow through! He screamed himself to sleep on the floor behind the door, but next morning was fine, not scarred for life and still says he loves me!
Second night, took about 10 returns and put himself to bed. Last night went straight off to sleep. In fact he slept 12 hours and I had to wake him so he wasn't late for pre-school. Fingers crossed for tonight, about to put him down.
We had a stairgate on his room until he climbed out over it. Before he learnt that trick, he would play if he wasn't tired enough to sleep and then put himself to bed, so that worked to a point too.
After 2 weeks of no routine which hasn't helped anyone, I'm determined to get him to bed. I have to be honest he's been much better behaved since, so that's a bonus.
Good Luck.