Despite the undoubted appeal of Guadalcanal, I've always favoured New Guinea. It has almost everything going for it - a much bigger variety of aircraft of different air forces, Battle of the Bismarck Sea, several different areas of action - Milne Bay, Port Moresby and the Kokoda Trail, Lae, Buna, Rabaul.
Of course to do it justice, like The Slot, you'll need an enormous map area with very long flight times.