C# is quite impressive, especially in comparison to Java. If it had been released earlier, wasn't owned solely by Microsoft, and supported all major platforms equally, it could have been huge, even larger than Java. If C# had reversed roles with Java a significant portion of the world would have been more productive.
C# 1.0 was very close to being an exact copy of Java. To say that if C# had been released before Java it would have been more popular is nonsensical as it started life as copy-cat Java. Without Java there wouldn't be a C#. Later versions of C# added more features much faster than Java. Many Java developers have since moved on to Scala and other JVM languages which are more expressive than C#.
