I think it's more of a personal preference which I attribute my dislike of this novel to. Fitzgerald isn't a bad writer, by any extent of the word, however, there are a few features which, personally, aren't very appealing.
First, the positives. Fitzgerald is fantastic at crafting settings; in particular, his wasteland. The barren area between the Eggs and the city is rife with symbolism, character development and crucial plot-points. Of the entire novel, T. J. Eckleburg was by far the most intriguing - religious symbolism has always been a point of interest for me.
Unfortunately, that was pretty much where the good points stopped for me. Mainly my problems were with characterisation. I didn't care much for Nick's narration. Though I realise it was a personal choice of Fitzgerald to make Nick more detached and uninvolved, even as a first-person narration, I can't help wishing he wasn't so lacking in depth. Gatsby himself, though lending his name to the novel's cover, seems far too ambiguous. His mysterious characterisation was extended so long that it lost almost any intrigue I had in the first place.
Overall, I don't regret reading this book. It was interesting, and held enough symbolism to keep me marginally engaged, though I doubt I'd re-read it unless contractually obliged or threatened in some manner.