Not sure. Simple imagination isn't always appealing -- I mean, the last 5 year old I talked to had a great imagination, but I was left with "WTF?" I think you need imagination, but the art of fiction is making the fake seem completely believable.

In writing more generally, however, I think the art is conveying impressions. Not just images, not just feelings, but the true sensation of life. Reading -- art, even -- is about experiencing things new and interesting, and if there isn't enough there (or good enough material) to experience something, it lacks appeal.