void Main()
{
    String str="count(\"xxx\") > 2";
    str=Regex.Replace(str,@"[^()]+\(""([^""]+)""\)\s*(\S+)\s*(\S+)","$1$2$3");
    Console.WriteLine(str);  //xxx>2
}

------解决方案--------------------

C# code
string temp = @"count(""xxx"") > 2";
                temp = Regex.Replace(temp,@"\w+?\((['""]?)([^'""]+?)\1\)\s*?(.*?)","$2$3");
                //xxx > 2