What specifically makes visual basic 6 a good programming language
when developing applications for windows? Are there any features or
reasons why it it beeter than java?

having learnt both java and VB 6 i would say that VB is easier to
learn and understand but thats my _opinion_

VB is a much simpler language which makes it good for rapid
application development or application prototyping prior to
development in a more complicated language such as C/C++.  VB is also
good to know because you can use it to extend other Microsoft
applications, notably Microsoft Office.  It will also help in learning
how to develop ASP applications because ASP syntax is pretty much the
same as VB.  Taking advantage of Windows components (ActiveX controls
and the like) is much easier.

On the other hand, Java is a more capable language.  The complexity of
the language makes it a bit harder to learn and application
development can take longer, but you have much more control over your
softare.  Java also implements a lot of modern programming concepts
that are good to know.  And Java applications aren't platform
dependant.

Hope that helps!