Look at the most basic level ppl wanted buy the iphone 5 for status symbol because it looked different then 4 and 4S. ppl always want a new model that they can easily differentiate. That wasn't the case with iPhone 4S and wont be the case with 5S. The interest in S models will always be less.
Not sure why even arguing this.. there a big air of disappointment with 4S was released because everyone wanted a redesign with bigger screen. Have you not compared the reviews of 4S to the 5? The 5's reviews are noticeably better.
But if you compared the non S vs the S, the S model wins. You're comparing a 4S to a 5, which are different body styles/generations. The 5 seems like such a huge step up from the 4/4S because they moved away from the 3.5" screen, and changed the 30 pin, not only that but it weighs significantly less, thus why the 5 had more people wanting it. Just like when the 4 came out, people went crazy because it was a redesign.
But when the 5S comes out, it will be superior to the 5. Faster, more features, kinks worked out, some sort of feature that the 5 wont have.
So if you think about it, being on the S cycle, even though you are getting a phone that physically looks similar to the previous, it is the BEST model out of the two, specs wise at least.
I'm on the S cycle only because my first iPhone is my 4S. Do I feel that being on the S cycle sucks? Absolutely not. Not saying that I'll be on the S cycle forever, but at this point in time it makes more sense.
There are also those that upgrade every year, which I personally could never do. I think every 2 years is the best way to be 'wowed' by the upgrade every time.