I hated the idea of Brussels sprouts, solely on reputation alone. Then I had them properly cooked (roasted) and dang, you can eat a whole plate of those for dinner! I kind of think that nearly every food on the planet has a way to make it taste amazing; some stuff, like chicken, can be made a million ways & still come out good, whereas others (like Brussels sprouts) require more specific techniques, otherwise they can be fairly unappealing. Roasting can make things like cubed butternut squash & even broccoli crazy amazing, whereas otherwise you might simply never care to eat them ever.
Spam was another one; I always thought it was a "joke" food that only sailors ate. Cut that into thin strips, fry it up, and it's actually pretty amazing. Spam musubi is awesome too, as are Spam, egg, and rice bowls.