It all depends on what is available and fresh.
As a baby, we spent summers in Welfleet on Cape Cod. Family legend has it that my first solid food was a steamed clam someone dropped and I picked up. My Mom wanted to take me to the hospital, my Dad wanted to give me more. We ate steamed soft shells (those obsene looking ones) because they were free and fresh and I learned to dig clams by the time I was three. Mussels were trash you wouldn't feed to a dog. Oysters were a specialty item out of our reach. Hardshell clams were Quauhogs you bought on the wharf and used to make chowder.
As a young man in New York, all seafood was expensive and of questionable origin. Still, sometimes fish is a must. I discovered that oysters, when no more expensive than clams and usually fresher, are a great treat. (With proper refrigeration, oysters hold much better than clams.) And I found that mussels, prepared in a shallot wine broth, or in a southeast Asian broth with lemon grass, have an assertive but sweet ocean flavor that holds up to seasoning.
I still love steamed soft shells no more than a day or two out of the beach, dipped in melted butter. And I love them fried. Fresh they have a delicate texture and flavor that is incomparable (and nothing like the chewy strips of sea clam). But if I'm at a restaurant that is not specifically known for perfectly fresh seafood I'm as likely to order something like mussels marinara.
IMO most people who aren't big on shellfish do like scallops, which are readily available in most areas, although usually better near the coasts. And if you ever have a chance to eat raw scallop and roe straight from the water, you'll know what real scallops are.