I had a SGS2 and have a SGS4 now. They are fine phones. I want a replaceable battery and a SD card slot. This reduces the field for me a lot.
For my wife I bought a Moto G and I suspect I will replace my SGS4 with a phone in the same class, once it needs to be replaced. Phones are rapidly approaching the phase where most middle class phones are good enough. Two years ago a high-end device was necessary for a good experience, these days this is no longer true.
Life will become tougher for phone manufacturers.