Since lemons were considered tropical in New Leaf, and New Horizons will be set on an island -- I'd love to have them as the native fruit! If not, apples always look very pretty.
Assuming there are no new fruits introduced, I'd like to have pears or apples this time around. I don't think I'd reset for them, but it would be nice.
Personally, I'd like peaches. Peaches are always so cute because they're pink and look so soft. The way they're detailed, as we've recently seen, they look almost like they were colored with colored pencils, which make them even prettier. I just hope they add a leaf again, since without it, they look a little bare.
Eventually I'll probably want all the fruit, but peaches for my native fruit!! I also hope they give a little more detail and definition to the cherries, they really look bland in their comparison from New Leaf.
I've never really loved the whole idea of the native fruits, especially when it impacts the perfect fruits. I want to grow perfect fruits of all types!
If I had to choose, lemon, cherries, or grapes. I especially love perfect lemons and perfect cherries.