Back when I was a child fish was so plentiful, and cheap, that we at fish two or three times a week. If you wanted you could find guys selling "a fry" outside most pubs. And in one if my first jobs in Freight Forwarding as we shipped fish to various countries getting some free fish was a regular occurrence. The result is that I am a big fan of fish, but am also always shocked at the price of fish these days, and don't eat it as much as I should.
As to my favourite fish, that's difficult. Love herring, salmon, tuna, skate, turbot, but overall it has to be haddock. When It came to the "freebies" from the fish suppliers it was a standing joke that ic one of our sales guys wasn't really liked he'd get a pack of cod. If he was appreciated it was haddock. To this day I will avoid cod which is still seen as kind of second class fish in most of Scotland, or at least in the North East.