Frasier contained the best of British-style sarcasm/irony, which helped make it endearing.
I love Frasier - as with all sitcoms there are a few flat episodes but generally the standard is very high.
If I were to pick favourite episodes, off the top of my head I'd go for "Ham Radio" and "The Ski Lodge".
There's an excellent oral history of the Ski Lodge episode from a couple of years ago:
https://www.yahoo.com/entertainment/frasier-ski-lodge-oral-history-164309203.html
Had a massive crush on Roz too...still do actually.