I'm fascinated by the differences between commercial fiction and literary fiction. I tell my students that commercial fiction is more plot-driven and is more "popular," read by the masses. And that literary fiction is usually more character-driven, and feels more "intellectual" because of the language and descriptions. It takes its time, and seems to be less concerned with pacing.
To me, the greatest novel would be a blending of the two - the faster pace of a commercial-fiction plot combined with the higher prose of literary fiction. I don't know if that's possible to reach, but a few come very close (Elizabeth Berg, I think, is one).
So, what's more important? Pretty, thoughtful language, or a solid, well-paced plot? I think it depends. If John Grisham inserted flowery descriptions or thoughtful character analysis, it would bring his plot to a standstill. On the other hand, if Anne Tyler focused more on plot and pacing, it's possible her books would lose some of their intellect and depth.
Yesterday, I read an interview of a well-respected book editor, Chuck Adams (link). What struck me is that he, an experienced editor, advises writers to get out of their own way and just write the story. Because, in a sense, story trumps language. Now, granted, he tends to lean toward more commercial fiction, where story feels more important. But, you know, I think what he says applies to ALL writers, commercial or literary. Because what he's saying is, don't be so proud of your well-constructed sentences, your pretty descriptions, that you lose sight of the story. Pretty is fine, as long as it doesn't get in between your reader and the book.
Here are a couple of excerpts from his interview. Fascinating!
I believe very strongly that books are not about writers, and they're definitely not about editors—they're about readers.... If the writing is poetic and so forth, that's nice. I'm reading something right now that has an amazing voice, and I'm only fifty-six pages into it, but I'm already getting a little tired because it's so nice, if you know what I mean. It's so pretty. It's like every page is a bon bon, and I want a little break somewhere. It's become self-conscious, in a way. I want the author to surprise me and excite me, and so far he hasn't. He's just made me think, "Oh, that's nice."
[Writers] think about making themselves sound smart and good, and they forget that this is really all about telling stories. I used to joke that I was going to put a big sign over my desk that said, "Quit writing and tell me a story." The problem is that they just write. They fall in love with their own voice.