Unless you live in front of the sea, frozen fish is almost always better.
Tomatoes can improve substantially if left without refrigeration, it's one of those fruits that continues to ripen after being picked.
I think there was a Good Eats episode, that tomatoes actually lose flavor if refrigerated - some chemical change, don’t remember the details.
Does it regain the flavour in the same way chocolate does when brought back to room temp, or does it lose flavour permanently?