Everyone seems to think that Frasier is happy being a Mountie. But I don't know if he is. I think what he wants (even if he doesn't recognize this in himself) more than anything is to be able to let go, but he won't let himself. He ALWAYS has to do his duty, he has to do the right thing, he can never let a crime slide, he has to pursue it. But I don't think it makes him happy. I think it makes him lonely. I'm sure he became a mountie because of his father, and it's entirely his father's influence on him.
Bob's ghost kind of acts as Frasier's moral compass, which is ridiculously skewed. Think of Letting Go, when Bob's advice was to get back on his feet right after being shot. Or in Victoria's Secret, when he tell's Frasier that he did the right thing in turning Victoria in. Bob says what Frasier thinks he should do - it's the criticism of "you're not strong enough, you're not good enough, you have to do your duty... ad nauseum." North is another episode like this.
Although this trend ends as the writers seem to decide to make Bob an actual ghost rather than a manifestation of Frasier's crazy.
Point is, Frasier never thinks he's good enough, and I think that that's why Ray is good for him - he reinforces the idea that Frasier doesn't HAVE to do his duty all the time, that there should be limits, that he can let go of the mountie-ness once in a while.
And that's also why I personally believe that the best moment of Frasier's life was running after the train in Victoria's Secret, where the mountie just shatters away from him, and he's free. For about thirty seconds.
I'd say that Fortitude Pass isn't in the running because he was probably killing himself over whether to turn her in or not the entire time.
However, the happiest period of Frasier's life is probably late season 2. Because you can tell that Ray is getting to him, cracking his shell a little bit. Not violently, like the moment he starts running in Victoria's Secret, just persistently. Ten years with Ray, and Frasier might've been almost as happy as a normal human being.
But man, I'm just a terrible romantic when it comes to Frasier and Victoria. What is it with me and doomed relationships? It must be my cynical side coming out.