Google, Microsoft, and AWS are in fight for the Cloud and recruiting top talent. One way to judge how good their cloud is based on how good their employees are. To get a peak into the employees you can use Glassdoor like Forbes did to discover whether employees would recommend working for the company. For these top guys here are is one set of data. 90% of google, 77% of microsoft, and 66% of AWS employees would recommend to their friends to work there.
You can go through the list to come up with where the rest of the cloud guys show up.
These results can give you an idea of the ability of each of these companies to recruit which allows them to build for the future.