I thought there was a discussion about HBO a few days ago. You need to have HBO to get HBOGO, correct?
Netflix has the largest library though, right?
But Amazon is a monster company. I'd imagine they will eventually surpass both Netflix and Hulu.
I like Amazon Prime the best. I had them all, but got rid of HuluPlus a few months ago. I find more on Amazon than I do on Netflix (tv series are the exception to the rule).
The key to Prime is that the video streaming is really a bonus. The two-day shipping on everything for a whole year is the real kicker there.