The most successful fruit is one that animals can see, enjoy the taste of, and don't eat the seeds inside. This way animals take the fruit and leave the seeds spread around for more of the same plants to grow. In that way, fruit is 'designed' to be taken by animals so that its seeds are spread.
So the way fruit looks, in the natural cases, depends on the local fauna.
For instance, as described on this page about the coevolution of birds and fruit:
plants have evolved conspicuously colored, relatively odorless fleshy fruits to attract the avian dispersers of their seeds.They are coevolving in response to the finely honed visual systems of the birds; plant species coevolving with color-blind mammalian seed-dispersers have, in contrast, dull-colored but smelly fruits. The bird-dispersed plants often have evolved fruits with giant seeds covered by a thin, highly nutritious layer of flesh. This forces the bird to swallow the fruit whole, since it is difficult or impossible just to nip off the flesh. In response, birds that are specialized frugivores (that is, that do not take other kinds of food) have evolved both bills with wide gapes (so they can swallow the fruit whole) and digestive tracts that can rapidly dissolve the flesh from the large impervious seed, which then can be regurgitated.
This page also goes into some details about the different characteristics of fruits and how those relate to particular types for animals.
There are also the unnatural cases.
Not some unholy undead fruit, but rather a human cultivated crop. An excellent example is the banana. The common banana found in the grocery store is a fruit guided by natural selection to look quite different from its natural counterpart.