What is the equivalent of AWS elastic beanstalk in GCP?

Question

Is Elastic beanstalk of AWS an answer to GAE of GCP?

Yes, in a nutshell, you can think of it like that.

There's an article by Google showing side-by-side comparisons of AWS and Google Cloud products, listing them as IaaS and PaaS:

Service     AWS                             Google Cloud Platform
-----------------------------------------------------------------
IaaS        Amazon Elastic Compute Cloud    Compute Engine
PaaS        AWS Elastic Beanstalk           App Engine

However, it is worth noting that at least AWS Elastic Beanstalk is not strictly a PaaS solution, I would describe it more as a management layer on top of EC2. From their FAQ:

Q: How is AWS Elastic Beanstalk different from existing application containers or platform-as-a-service solutions?

Most existing application containers or platform-as-a-service solutions, while reducing the amount of programming required, significantly diminish developers’ flexibility and control. Developers are forced to live with all the decisions predetermined by the vendor–with little to no opportunity to take back control over various parts of their application’s infrastructure. However, with AWS Elastic Beanstalk, developers retain full control over the AWS resources powering their application. If developers decide they want to manage some (or all) of the elements of their infrastructure, they can do so seamlessly by using Elastic Beanstalk’s management capabilities.

I don't think it's possible to compare these platforms with benchmarks. There is still a lot you can configure on this platforms and performance will mostly depend on your configuration and (even more) your application code.

It comes down to differences in pricing, easy-of-use and the availability of other services on these platforms.