Which iPhone was the first to really take off?

iPhone (2007)
iPhone 3G (2008)
iPhone 3GS (2009)
iPhone 4 (2010)
iPhone 4s (2011)
iPhone 5 (2012)
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A total of 13 votes were cast: 4 girls and 9 guys. See detailed results
Which iPhone was the first to really take off?
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