It's not a question of whether or not an exceptional programmer can program exceptionally in any language. It's a matter of which language provides them with the best tools to program exceptionally faster than the other exceptional programmers.

You mention COBOL. For writing complex applications on a modern OS, it's pretty much a given that certain languages are worse than others. COBOL vs. Java, for example. So, since certain languages are worse, then other languages must be better. Java vs. COBOL.

While it's not a given that there will be a winner, even in a specific realm like web applications, it's clear that there will probably only be 2 or 3 languages/toolsets that simply are better than the rest. And, that group will change over time. Ruby-on-Rails is an excellent example of this. When Viaweb was started, Ruby barely existed. Now, it's one of the top web languages for the cognoscenti, specifically because of ROR. One can churn out amazing applications with little effort on Rails, making it a very productive language to work in. (Perl has Mason, Catalyst (the successor to Maypole), OpenInteract2, CGI::Application, and others to do what Rails does.)