Sweet olive followed by hibiscus.
Sweet olive because I love the blooms, and hibiscus for the leaves. I wish the bushes bloomed more overlapping though, I think I would like others more if the colors were more visible at the same time.
Hydrangeas followed by holly. I like hibiscus bushes too mostly because you can buy multiples of them at a time when they're on the island, so it makes decorating with them easier than any of the other bushes.
I think my favourite type of bush is the sweet olives. I would have lined the paths in my town with them but I wanted to alternate colours so I ended up choosing azaleas instead ><. I kind of regret it now but I am too lazy to re-bush my entire town and I'd probably need 300+ sweet olive starts, haha xP.