Let me draw you a diagram:
That's basically how I see literature. Three (overlapping) categories: the Good, the Fun, and the Bad. Simple, eh?
The Bad is pretty obvious: that's the crappy stuff that really don't want to read. It might be terribly written, or horrendously derivative, or maybe just boring. Ending up in the (tiny) overlap between the Bad and the Fun is pretty much always an accident -- I don't think you can really aim to fall into that bit.
I'm going to struggle to describe what should go in the Good circle, but I'm sure you know it when you see it. This is the circle in which (I think) authors of literary fiction try to land. For me, lots of different types of books fall into this category. Things I actively enjoyed (Extremely Loud and Incredibly Close  by Jonathan Safran Foer). Things I admired, even if I found them difficult (The Road  by Cormac McCarthy). Even things I disliked, but recognise as objectively Good, or at least important (I'm looking at you, Moby Dick  by Herman Melville).
Fun books are something else again. These are books that aren't going to win any great literary acclaim, but which you really enjoy reading. I think a lot of people's favourite books fall into this category. I also think this is where a lot of genre fiction lives. Alastair Reynolds is an excellent example -- I really love his stuff, but I'm (probably) never going to suggest we should be giving him the Man Booker Prize.
Which books end up in the Good/Fun overlap is, I suspect, even more subjective than the other categories. I'd put most of Charles Dickens' stuff in there, but I doubt there are heaps of people these days who would agree that Dickens is fun. Some examples of genre fiction I'd include here are The Dervish House  by Ian McDonald, The Scar  by China Mieville, and The Quantum Thief  by Hannu Rajaniemi. I wouldn't be surprised, though, if other people shunted them out of the Good/Fun overlap into one category or the other (although I'd get punchy if you tried to shift them over into the Bad category!).
So why am I going on about this? Well, I really want to believe that the Good and the Fun categories are both (equally?) valuable. I'm pretty sure I believe it when I'm reading -- I loved The Dervish House, but its good-ness didn't make me enjoy the very fun Dust  by Elizabeth Bear any less. I have real difficulty internalising it, though, when I sit down to write.
Obviously I'm not expecting the things I'm writing now to be worthy of the Good circle. It's far too early for that -- I've got a lot to learn, and lots of practice to do. The problem is I have difficulty believing that anything I ever write will be worthy of the Good circle. That makes it difficult to get motivated; no matter how hard I try, I will never, ever be Ted Chiang. And if I can't ever write anything Good, why bother writing at all?
I have to keep reminding myself that there's that big circle in the middle, filled with many of my favourite books, that is just as worthy as the scary circle on the left. There is nothing at all wrong with writing things that are fun. If I concentrate on doing that, maybe I'll be lucky enough to occasionally sneak something into the Good/Fun overlap. But even if that never happens, that doesn't (necessarily) mean that I am a bad writer. That, after all, is what the circle on the right is for.
I want to finish up by saying that there's another reason, aside from the navel-gazing, that I decided to talk about this here. I think the little Good-Fun-Bad Venn diagram provides some useful insight into the reviews I write. I'm really scoring on two different, but overlapping, things: how Good a book is, and how Fun it is. Which category you consider most important is, I think, a matter of taste. And, importantly, I don't consider books that fall into the overlap between Good and Fun to necessarily be superior than books that end up in one category or the other.
(Also, I just wanted to draw you a diagram.)