iMAC has a 10 years design... GREAT design... they didn't change it (upgrade a bit).Says who? For all intents and purposes, the best iPhone designs were 4 and 5. And they were good for THAT time they were released. If you also want to ride a 1940s beetle because of its iconic design, go right ahead.
5S was an iteration that stuck out because of the introduction of gold, and 6 resulted in epic sales, even if a bit meh from the get go.