Those aren't really alternatives to GAE IMO unless you would also say that a laptop is an alternative. A real GAE alternative would be a hosted solution that doesn't require you to install an OS or even know what OS it's using.
AWS has Elastic Beanstalk. Azure is still finding their own PaaS pathway.
Cloud Foundry gives you the "just push" experience for both of these (as well as vSphere, OpenStack, GCP and more to come). It's open source, with the IP owned by an independent foundation.
Disclosure: I work for Pivotal, we donate the majority of engineering on Cloud Foundry.
Within Google, either of the GCEs (https://cloud.google.com/compute/ https://cloud.google.com/container-engine/) depending on your architecture.