Phone wise, right now, the 4s and SGS2 is a fair comparison. According to wikipedia, SGS2 came to sprint on 9/16, att on 11/6 and tmo on 10/12/11 while it launched all over europe and asia in May and June of 2011. That gives it a good 3 or 4 month lead time to get into the market before the 4s is launched on 10/14 if it was allowed to come to the US at the same time.
Especially considering a new iphone comes out every year and the rate which new android phones are coming out, that is a good 40% into the "current best offering" life of the phone already.
Better phone debate aside, I feel like that lead time could have made a significant impact on sales when at the time, we would be comparing the SGS2 to the regular 4. Too bad the US gov lets our telecoms screw us over, and not just for the SGS2.