The comparison between Microsoft’s C# (programming language) and Sun's Java (programming language) is a common water cooler debate. Here's my general approach / thinking:

C# and Java are both descendents of 'C', are based on the object-oriented paradigm and were based on the best programming principals / innovations of their time.
Time in the computer industry moves at a rapid pace, new ideas, changes, innovations can seemingly happen over night.
When Java was released (in the 90s) it was one of the better languages, now 16 years later C# is one of the better languages (C#’s original release date was in 2001 a minor revised version was released in 2005).

Microsoft's C# is NOT a copy of Java, but it does bear resemblances to most object-oriented programming languages (including Java). Programmers at some point recognize that programming principals (and in this case the object-oriented paradigm) transcend specific languages.

“Once a programmer realizes that programming principles transcend the syntax of any specific language, the doors swing open to knowledge that truly makes a difference in quality and productivity.” - (Steve McConnell, Code Complete 2nd Edition)

Read more on Wikipedia : the Comparison of C Sharp and Java