I thought it was weird how different the character was between shows. Cheers Frasier would probably beat up Frasier Frasier.
I actually felt that was fairly justified - a lot of a person's behavior is determined by their situation in life. In Boston, Dr. Frasier Crane was married to a cold but beautiful colleague, had a rather successful practice, and spent most of his free time in a working class bar drinking generic beer, rubbing elbows with people he could look down on in a friendly manner.
In Seattle, he was a radio talk show host, divorced, living with his dad and having his even less manly brother as his closest companion. He spent time at a cozy little cafe drinking gourmet coffee from demitasse, often alone.
Cheers Frasier was successful, more than most of the people around him. In Frasier, he wasn't - he wasn't doing poorly by any means, but most of his social circle was comparable to him. Aside from the fact that he was a divorced dad who rarely got to see his kid, well, I'm guessing that effected him and he dealt with it by becoming more introverted and elitist.