Now, you've got me thinking about a topic I might have already touched upon here.

First of all, regardless of which ocean or sea, there seems to be an inverse correlation between water temperature and deliciousness for most varieties of sea food. For example, New England and the east coast of Florida share the same ocean, but the former has more fish species, and fatter (i.e. more flavorful) fish intra-species.

As for Atlantic v Pacific, I might be slightly biased due to spending my formative years on Cape Cod and in Boston (divorced parents), but I found the fish selection and quality there was generally much better than California/Oregon/Washington. For example, at most normal grocery stores on the West Coast, you're limited to salmon, halibut, tilapia (yuck!), and maybe something like Dover Sole. Higher end markets have a bit more variety, but a lot of the good stuff isn't local.

Meanwhile, in New England (as well as France/England), you could easily eat a different type of fish every day of the week. As cliché as it sounds, cod (especially haddock) is actually my favorite fish from Cape Cod Bay, but I also like flounder, bluefish, striped bass, black sea bass, etc. I don't care so much for swordfish myself, but it's also popular, and I would always choose it over mahi mahi (which has similar flavor and texture profiles).

Within the Pacific, I'd like to make a specific recommendation for Hiroshima (and nearby cities) if you like ,sushi because the Seto Naikai Sea has outstanding fresh fish (e.g. yellowtail, red snapper, sea urchin), especially during colder months. When you eat sushi in Tokyo, the variety is obviously the best in the world, but odds are it has passed through the The Tsukiji Market, which adds at least a day in terms of (un) freshness.

I partially overlook my anti warm water bias when staying on beaches in certain parts of Southeast Asia where fresh fish comes in every evening. Sea bass, red snapper, and white snapper seem to be common, and all taste fairly similar to me. What I really like, apart from the freshness, is that you can usually have it prepared according to your tastes (personally, I like to bring a little bit of non-terrible white wine myself, and sometimes olive oil).