Agreed, but I might place Hoshi no Koe one step higher than Promised Place. Just because he did it in almost all entirely by himself, which is one hell of a feat. And the ending is so damn moving. Can't wait for Shinkai's next movie, whenever that may come.
btw, I'd recommend all his movies, but if I'd had to rank them I'd say 5cm per sec > The Place Promised in Our Early Days > Voices of a Distant Star. And he actually varies with his story a lot more than you think event. You'll just have to watch and see