I'm not going to deny that I'm an unrepentant snob when it comes to FPS games.
I like them on my PC, I like them pretty, and I like them 'splodey in all the right ways. A well made shooter is almost a thing of beauty.
In terms of pure design, I hold Unreal Tournament as the apex of what a shooter should attempt to attain. MMOFPS games have to do double duty, since they not only have to work as an FPS but they also have to properly convey the persistent world of an MMO. I didn't have an opportunity to try Sony's original Planetside, but to correct that oversight, I did get the chance to go through Planetside 2. I can't really speak to its value as a sequel, but on its value as an MMOFPS, the first half seems to be fairly well executed at the expense of the second.