The 4S isn't selling for anywhere near what the iPhone 5 is on average...not even close.
As far as "made the best", are you asking about the phone itself or the operating system ON the phone? The 4S was very well made, so I have no argument there...for a device with a full glass back (one that I thought would scratch like crazy), it was surprisingly durable. That said, I prefer the build quality of the metal iPhones, they remind me of my Macbook Pro, and to me, the materials used on both feel like a better quality build than the 4S's glass panel back...the fact that the 5 and the 5S are a more singular piece than the 4 or the 4S supports that for me as well.
Then we have the camera...the 5's camera was amazing, the 5S's camera is phenomenal. At no point on previous iPhone's was the camera even close to this good...not even in the same ballpark. Light weight, battery life, slim form factor, LTE...I mean I could go on and on about the features.
The OS is really nothing to be compared to be honest, in my opinion, because the 4S was running a slightly updated iOS version...it was not completely renovated, it was not upgraded as much as iOS 7 was...it was truly a more polished version of the old, vs. iOS 7, which might as well be an entirely new experience.
And regardless, there are no issues with the iPhone 5 as far as running the OS, the bugs and glitches and what not are not a problem of hardware, they are solely within the software...as was the case with the 4S (good or bad)...so trying to decide which iPhone was the "best" should not be relevant to the OS it was using.