I disagree. From what I can see, the gap between Samsung's flagships and the rest of the field has widened in 2015, compared to that of 2013. In 2013, the S4 was not that special compared to other phones like HTC One, LG G2, or Moto X. The S4 had a little better specs here and there, but nothing was meaningfully better. On top of that the S4 was loaded with tremendous amounts of bloats.
Fast forward to year 2015, there is a clear dividing line between Samsung's flagships and the rest. If you compare the S6 and the Note 5 with Motorola, HTC, LG, Sony's offerings, the difference cannot be starker.
- S6 and the Note 5 use the latest AMOLED screen. The rest of industry is still using 2013-level LCD/AMOLED.
- S6 and the Note 5 have vastly improved cameras, often ranked No.1 by many, and the rest of industry hasn't moved much from their 2014-level offerings. (except for the Nexuses this year)
- S6 and the Note 5 avoided the disastrous S810. All S810 phones I have seen other than the Nexus 5X/6P are a mess. And Google got the S810/S808 to work by really aggressive throttling. A57s on my 5X will throttle within 5 minutes of anything intensive, and completely shut off by the minute 10. Exynos never throttles at least during single-core tests and runs cooler.
- S6 and the Note 5 has a build quality that is unmatched by the competitors. Whaever one thinks of their designs or material choices, build quality can be evaluated objectively. Here the competitors are at 2014-level of fit and finish. And at least in the U.S. I do not see them catching up to Samsung's build quality anytime soon unless/until Chinese OEMs enter the U.S. market.
- I know designs are subjectively judged, but certain aspects can still be compared. Such as ergonomics, location of buttons/sensors, as well as size and weight. Samsung is leading in this regard as well, IMO.
- There are other value-adds, such as fast wireless charging and fingerprint sensors. I know people have vastly different opinions on those. Nevertheless, they are useful extras for those who want them at no cost to those who do not want them.
All these merits are worth $100~200 premium over the competitors' products from my perspective. I mean, it would be strange if that weren't the case.
Whether Samsung sell more phones or not is not my concern, but if they sell fewer phones, I think that has more to do with the overall smartphone landscape, i.e. arrival of good-enough performance and market saturation, not because Samsung products lack merits.