You know how bright fruit are good for you? This is because there's not only protein, potassium, carbs in the fruit (that are certainly good for you), but there's also vitamins, polyphenolics, flavonoids, etc. (complex plant metabolites) that are good for you too.
Fruit skins tend to contain more of these things that the fruit pulp ('tend', exceptions are obviously there), so some of the dessert (e.g., watermelon, bananas) fruits don't give you as much bang-for-the-calorie.
Banana is probably the best example. It's miles better than a candy bar, donut, and maybe even a PB&J sandwich. But there're better fruit choices. In general, fruits that include skins are better. Fruits that have been 'recently' bred to maximize sweetness aren't going to be as good. Ostensibly, tropic fruits are pretty good, because they've evolved to be in symbiotic relationships with primates (but their main contribution is easy calories).
Antioxidant theory isn't very good, but antioxidants seem to be a really good proxy for whatever is 'good for you' in fruit. This not really due to the fact that they scrub Reactive Oxygen Species, but more because they interact with our metabolisms in ways that we like.
The epidemiological association between health, well-being, and plant consumption (veggies and fruit) is pretty robust and is there for a reason.