Apple took the smart phone from something used by technologists and other tech oriented people, and turned it into a mass market appliance accessible to everyone - every smart phone that has come since is related to it in form and function.
edit: just to clarify. I do agree that the iPhone deserve a place in the history books because it did change the landscape significantly. But my point was that the iPhone wasn't the first phone of it's ilk (probably the best all rounder and definitely best at specific criteria, but those are point I'm enjoying discussing here). In light of that, if the iPhone deserves a place then equally the handsets that pioneered much of the technology and paradigms which Apple beautifully combined, those other handsets deserves a mention too (like how scientific papers based on original research still need to draw from the pool of existing research and thus even new theories owe credit other publications)