Say what you will about the cloud market, but you have to acknowledge that we are still in the very early days from a pure market-size standpoint.
That means you could say that AWS has a huge marketshare lead, and you would be right. You could say it's mostly a two-horse race between Amazon and Microsoft at the moment, with Microsoft a distant second — all correct. You could say you can barely see Google in third or fourth place with single digit market share — and you're spot on once again.
But don't let that fool you. Google is a viable and dangerous competitor to AWS, maybe in some ways more so than Microsoft and certainly more than IBM. That's because Google was born in the cloud, has always had the cloud chops, but has never quite gotten it together to build a viable enterprise cloud business.