I use all three and each of them have a different purpose. I use Netflix to watch movies and TV shows that have been out for a while or that have been recently added. I use Hulu to watch strictly TV shows (i.e. House, SNL, The Office, etc...). And I use Amazon Prime to watch other movies and shows that Netflix doesn't offer. I've been using Amazon a lot more lately because I can instantly buy the new episodes of Walking Dead, How I Met Your Mother and Big Bang Theory as soon as they are aired on TV.
I personally wouldn't say that any of them are "better" than the others. They each have an area where they shine. I would have to say though that Netflix has gone down a lot since it first came out. After there increase in price and the splitting of renting movies and digital movies, I'm greatly considering stopping my service. I would greatly recommend it for children now with all the new kids movies and TV shows they have released.