This isn't my specialty, but I suppose the list includes Microsoft's Windows Azure and the Google Cloud Platform. There are some open source efforts to watch as well, including OpenStack (backed by Rackspace and others). No doubt I've missed some.
There's plenty of time for those competitors to catch up to AWS by 2020.
Very true, but this fails to take into account that Amazon will not stay stagnant till 2020 for competitors to catch up.
Because Amazon already have a healthy majority of the users/marketshare, they are perhaps better positioned to understand and innovate upon the future needs of these customers, and keep building their product offerings by anticipating where the "puck is going to be."
With that said, nothing is set in stone, so competitors might as well overtake AWS by 2020, but if I had to bet my money, I'd bet it on Amazon.
:)
None of these have the wide product functionality that AWS has -- yet. Amazon has a multi-year head start on most of these companies, but as you mention, there's lots of time to make progress before 2020.