Well, it's kind of like the difference between Matrix 1 and Matrix 3...;) Movies are all utterly linear, which has no bearing on their entertainment value--there are good movies and poor movies--but they are all 100% linear. In Matrix 1 we got an interesting story along with characters easy to become involved with. By Matrix 3, however, the story and the characters became submerged in a sea of mindless special effects and superficial technopop art that was only pretending to be concluding saga of the story begun in Matrix 1 and the end movie was certainly a big disappointment to me. The idea that a fps cannot be entertaining and involving on emotional and intellectual levels simply because it's "linear" is ridiculous, I think, and is no more true for a fps than it is for a movie.
It is well known that I cannot err--and so, if you should happen across an error in anything I have written you can be absolutely sure that *I* did not write it!...;)