I went through that with Ash when I decided I was tired of going to bed when she did. Granted she was a lot younger (8 months? Maybe? I can't really remember) but it really did take a lot of soothe, back up and stay within view, come back if she cries, soothe her, back up, repeat repeat repeat.. She got tired eventually.

We did it when we first put her in her own bedroom too, except I could leave the room..just had to come back in a LOT at first.
Takes work, time, and a whole lot of patience..but if you stay persistent, eventually he'll realize he won't spontaneously implode the second you leave his sight at bedtime