The question asks "what is the best fruit?" - but the answers only show you what the most widely available fruits are.
Anything that's lesser known or more expensive to mass produce or harder to ship fresh - is a complete non-starter to begin with, regardless of how good it is.
Her favorite childhood berry was the mulberry - a berry completely unknown to me. Out of curiosity, I tried getting mulberries - but since those grow on trees which only start bearing fruit after 10 years of growth (!!!) - those can't be produced at a commercially viable price point.
It wasn't until years later, that I found a mulberry tree in an old cloister garden, of a cloister that specialized in preserving old strands of plants that were no longer being commercially grown.
They are really tasty! If they were actually available, I could easily see them become just as popular as other berries.
That doesn't seem to follow. If nothing else, there are a lot of existing mulberry trees.