You could compare Digital Ocean to Amazon Lightsail. or to Heroku. But Lighstail is only one of the many services provided by AWS.

If you only see some easy to use servers, then you could compare and decide. If you need these servers to be part of a larger solution, with complete control of your network topology between your instances, with massive scale databases, fine-grained permission policies, dedicated link with your on-prem infrastructure (hybrid cloud), audit logs for compliance reports, 'infinite' object based storage with crazy data durability (the famous S3 eleven 9s), and some CDN solution, plus some serveless features, plus this, plus that (I won't list them all, there are hundreds of services and features)

In short, AWS could be compared to Google Cloud Platform or Microsoft Azure.

For any other solution, you're only going to compare it with a small subset of one of these big IaaP/PaaP providers has to offer. And if you only need this, it might be a perfect fit for your current needs. (These smaller providers try hard to have a valid business model by providing some ease of use or optimized-for-something solution, because for the general use-case, they just can't compete any longer with the 3 big players.

It's not. I'd compare DO to a Linode or Rackspace.

AWS's closest competitors right now is Azure and Google Cloud.

I love Digital Ocean, but for enterprise Amazon Web Services might be better. They have a very useful feature that allows you to own the server, but the invoice is between Amazon and your client.

AWS offers a wide variety of services - just look at all of them on the AWS Console, they can barely fit my screen. It would be more appropriate to compare a specific service, say EC2 with DO. We (backendless.com) have done a similar comparison about a year ago when our EC2 bill started sky rocketing - we run a rather large server farm. After doing all the due diligence, we decided to migrate to OVH.com and saved between 80 to 90%.