Oh - we were so there...it was a long 9 months, but I think we are out of it now. And I look back and try to see the things that we did to change it, but I think we tried all the same things and she still struggled. Our problem wasn't that she cried, but that she just kept coming out of bed and coming downstairs.
A couple of things we are doing differently now, some of which might have contributed to the change but not sure are:
1. Talking about tomorrow - the fun things that are going to happen and what we are going to do once we have a "good snooze"
2. Talking about things to dream about
3. Putting a clock in the room and telling her that bedtime is 8:00 and we don't get up in the morning until the clock says 6:00
4. The bedtime routine list - we put together a list of all of the things that we do leading up to bedtime, decorated it and looked at it every night for a while with the last item being going to sleep. We used that for a month or so and then it stopped being helpful.
5. We tried music in her room but she got distracted by it - she was probably a little bit young at 2 1/2 so might help you?
6. Telling her what we are doing downstairs and that we are going to go to bed soon and will come check on her before we go to bed.
7. We really shifted our approach from "get in bed!" to "why are you having trouble going to sleep" and that helped a little bit. We stopped creating a power struggle, which I think was gearing her up more. Unfortunately it sounds like your son is gearing himself up so not sure how to handle that.
Our daughter's problem was getting out of bed and was driven by not wanting to miss what was happening downstairs. That is why some of these may have helped a little. Not sure if your son has the same things going through his head so not sure if these will help. But thought I'd send them along in case. I TOTALLY FEEL YOUR PAIN. I hope it gets better really soon! Good luck