before putting him to bed, do some fun activities that are phyically and cognitivly energy draining. then about an hour before nap time, start relaxing by reading quietly with him or wathcing a bit of tv (turning the volume down will encourage him to be still and relax quietly). It also helps i you prepere him for nap time. This could involve telling him that it will be nap time soon. that way he knows what is cominh next and he wont feel like he has just been rushed nto it.

 We have the same problem...  I would continue to put him down for a nap during the day kids need their sleep.  Tire your 2 year old out make sure he is tired.  I always make sure we go for a walk or do some sort of activty that will tire him our chasy etc....  

I found that it was a new thing for him and that it was just a game. I was sitting with my son during the day until he fell asleep, but I soon realised that this was becoming a habbit for him.  Wanting me there all the time.   I found that you have to be quite strict about it.   Keep putting him to bed like you have.   First time say time for nap/sleep give a kiss and walk out then from then on just stand at the door and when he comes out just put him to bed with out any talking or fuss.

We actually have our stair gate across his bed room door we prop it open and on the 3rd time he gets out we then say, if you get out again then the gate gets closed.  He hates the gate being closed and so will stay in his bed.  

Sure is a pain, I am going through the same thing at the moment.  Just keep trying and don't give up, this is probably what he wants.  If he is not going to go to sleep then he needs some quite time.

Hope this helps.