Android memory stack management loves stuffing ram with apps, but with 2GB it provides twice as much free ram than 1GB. That said, some issues are due to memory channel management. Examples are the current Tegra devices, which are pretty bad with bottlenecks and do result in issues that some may think are ram related.
Factor in a lot of games are huge and take up ram, plus the higher def displays like on the S4, 2GB is a need rather than marketing hype. Integrated chips like these use some of the ram for graphics.