Short and sweet since I have never done this before. Long story short i'm getting a better opportunity than where I am currently, but my current employer is kinda bitter about it. The reality is he lives in a bubble of reality he created for himself. I really hate to leave with that kind of situation, but I really don't know what I can do about it. Any advice?
EDIT: It's not to say that he was always bitter. He actually is a great guy and does a lot for his people. He is just in a tough spot, and me (as a key person) leaving is really hard on him... and I'm certainly seeing the bitter side of it.
I'm not so sure that is good advice. Your soon to be old boss usually is not prepared to receive "useful feedback". As cathartic as it would feel to tell them that "It would have been nice, even once, to hear you say 'good job' in the 3 years I was working for you." it's unlikely to produce any positive change for you or him. You had X years of employment to share that feedback if you felt it was important.