Thin or predictable narratives fail primarily because there's nothing within the plot itself to keep an attentive reader or viewer going. The only reason such narratives succeed is because they are coupled with something externally appealing (think Avatar's superior visuals) or because the kinds of people who engage with such stories aren't looking for anything else. There's nothing necessarily wrong with the latter of these two reasons; anyone who has worked an insanely busy schedule can understand the need to read something without having to make an effort to think deeply about whatever is going on (the same applies to movies). This is where popcorn bestsellers come from and why they exist: to serve a market niche that, more or less, has no interest in the production of literary (or film-erary) merit. They want a quick, simple read that engages, gets the job done, and can be set down without so much as a forethought. One need not look any further than the Harlequin Romance novels, which have predictable plots and, thus, predictable characters.
But, the greatest offender within fiction of any form (written or visual) is the illogical narrative. These are stories in which things happen for unclear or unknown reasons, without a logical purpose for that uncertainty; it would be fair to assume that some stories might have events which, from the beginning, seem to have no logic to them, but which might eventually appear to have an underlying logic--thus, appearances may be deceiving. Setting this notion aside, however, we can see that illogical narratives have a tendency to flirt with convenience. Things happen not because that is the logical way they should, but because there is a hole that needs filling or a shocker that needs exposing, neither of which contribute anything to the development of the character and create nothing but a bigger void in the narrative itself. I've made similar arguments about J. J. Abrams' vision of Star Trek here and here, in which one need not look any further for this discussion than everything following the introduction of future Spock: here we have two characters (present Spock and present Kirk) who have come to despise one another for entirely acceptable reasons, resulting in one character (Kirk) being left on a barren ice planet where, by some magic stroke of luck, he meets future Spock, who proceeds to tell him everything that has thus far transpired and why, and that present Spock and present Kirk should become best buddies, followed by a convenient journey to a nearby Federation outpost where the missing Scotty is found wallowing in a pit. Is it any wonder why I call this convenient?
The problem I see with all of this is that these sorts of convenient or illogical narratives exist in droves. Narratives have grown weak; so much attention seems to have been paid to those narratives that, more or less, don't make sense, or are too convenient, or have no reason to be the way they are. The same is true of predictable plots, of which Hollywood is the biggest offender, with its dozens of remakes and attempts at original stories that end up falling flat--adaptations deserve to be ignored for this discussion.
But why is this? What has happened to narrative that so many creators, whether in film or books, have resorted to playing with the same fire over and over? Some arguments could be made about executive control, at least in movies, but this can't be true of everything being produced. Certainly a factor in this is buyer feedback--if a book sells, more like it will be produced. But, again, this isn't the only factor. This problem is undoubtedly multi-factorial.
Beyond that, though, I have to wonder if illogical plots are simply the byproduct of flashy everything: ideas, visuals, and so on. We've created an industry (book/movie, what have you) that needs to produce the thrill of a new idea, world, visual, or whatever in order to move paper and fill seats. Audiences are clambering for Transformers 2, Avatar, and Twilight, because they provide something that maybe can't be found elsewhere--or at least can't be found is such an obvious and easily consumable form. Perhaps what is killing narrative as the dominant mode of expression is not so much a weakness in writers, but a weakness in the market itself, which has pushed for the production of desire in everything else but the narrative.
Books, we'd have to assume, are much safer than movies at this point, because at least experimentation is still being done within the literary community (including genre fiction, because I make no distinction between SF/F/H/M/R/C/etc. and "literary" fiction; the distinction is meaningless anyway). We are still seeing novels that push boundaries and try new things. They exist and sometimes sell well (China Mieville, for example, is remarkably experimental, even if it doesn't seem like he is marketed as such). But, maybe this explains why book sales, while higher than they have been since post-2000, are still not as high as they should be. The book is lagging behind, just slightly, on the illogical narrative and predictable plot front, while movies, with their infinite ability to do new things visually, continue to move away from narrative and towards something else. Now it's 3D; in a decade it might be some sort of weird VR experiment.
I worry about narrative. It's too important to forget, and the idea that we might one day leave it behind for something flashy, immediate, and short-lived in somewhat frightening.
But what would you do if narrative died? Or do you think it's pretty much safe and sound in its little literary house?