Firstly, your XML isn't well-formed so I'm surprised you can process it at all. In <container:enum> you are using "container" as a namespace prefix, but you haven't declared it anywhere (I would expect to see xmlns:container="some....uri".)
Let's imagine you solve that by getting rid of the namespace, so it reads
<parametervalues>
<enum>parameter1</enum>
<value>data<value>
You can now find the value of parameter1 using the path expression
/container/parametervalues/*[.='parameter1']/following-sibling::value[1]
However, this is a very odd way to design your XML. Why not use
<parameter name="parameter1" type="enum" value="data"/>
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference