For those who didn't like it because of the CGI and the soundtrack:
Well... with no CGI this movie would be boring. With no CGI they'd have to remake it entirely and they would have to put a lot more of dialogue and inside into the characters. I'd like to watch that version too.
However, I did like this movie. I think you have to be open minded about it. I hadn't read the book before watching it, and I think having read the book made it impossible for a lot of people to like it since they were expecting the movie to be like the book and they didn't want any changes. But I think, if you forget about the book and take the movie for itself without comparing it to the original source, it's a great film with fantastic acting and an interesting style (I agree though that the casting could have been better: maybe Sean Penn for Tom, someone prettier for Daisy and I don't know who for the mistress; DiCaprio and Maguire were ok I think, although I repeat I haven't read the book.
About the CGI and soundtrack: their purpose is to show the excessiveness of it, the 20s were a flamboyant, extravagant time and in Gatby's house more so. He wanted attention, he wanted Daisy to notice him. He wanted to show how important he was, he wasn't a nobody from nowhere anymore. Therefore the parties, the celebrated guests, the pink suits, the fireworks, the booze... The CGI wanted to exaggerate that even more, make it so WOW, every landscape had to be astonishing and the rap and hip-hop wanted to add to that (I don't like those genres at all but I liked the contrast -didn't Stanley Kubrik use 19th century's classical music for 2001 A Space Oddyssey -not comparing the movies, just an example-).