Let's be honest here, all fiction is speculative. If it is not true, the author made it up and it is speculative. Now, I take it you are holding out that the inclusion of 'super natural' elements (magic, faster than light travel, non human intelligent beings, etc) automatically means that the work is not worthy in you eyes, with a few exceptions. I argue that these are just elements of a story, and it is up to the writer to use them well. I will echo Larry's response, Tolkien is not a good example. I love The Lord of the Rings, but Tolkien does immerse himself too far into myth building to really focus on literary content. But it is one hell of a story.

The vast majority of all literature does not have high literary merit, and that is where your argument falls apart. You concentrate on one genre (I am lumping all sci-fi and fantasy together) and leave out the rest of the other junk out there. And let's be very honest, most of it is junk. People reference the so called 'classics' (both modern and true classics) and hold them up as if they are some kind of Holy Grail. However, on further review, these 'classics' were just a few of the works published among a load of BS in a given year, and have proven the test of time. It just so happens that many have either super natural of futurist speculation elements in them.

Having said all that, I do agree with part of your original premise, only reading one genre is rather dull and boring. I just take exception with your automatic response that this genre is different that any other in the amount of 'junk' that gets published.