You’ve really started something here!! 🙂
From a complexity and sheer ingenuity of design point of view my choice would be the Bristol Centaurus, Napier Sabre, or Rolls-Royce Vulture X….
But for classic engineering excellence and longevity of type and developement it would have to be the Merlin…nothing else sounds like it or evokes such a response from the public as a whole…the Griffon is a fine engine but always sounds like it it has a couple of plugs fouled!
Sorry if I’ve upset anyone… these are only my humble opinions! 😉