Can we create Fail over clustering for SQL Server 2012 standard edition on amazon EC2?
Yes you can deploy that scenario to EC2 just as you would if it was VMWare environment. However with AWS I would highly suggest you follow the guidelines on how to properly set this up from Amazon.


  AWS provides a comprehensive set of services and tools for deploying Microsoft Windows workloads on its reliable and secure cloud infrastructure, such as Microsoft Windows Server Failover Clusters and SQL Server AlwaysOn Availability Groups. WSFC clusters and AlwaysOn Availability Groups, together with Active Directory Domain Services (AD DS) and Domain Name Server (DNS) functionality, provide the underpinnings for many enterprise-class Microsoft technology-based solutions including Microsoft SharePoint and .NET applications.


https://aws.amazon.com/windows/resources/whitepapers/alwayson/