The term "critical aesthetic" has popped up several times in various writings on virtual world design that I've looked at recently. Is a critical aesthetic the same thing as a pattern language?

"critical aesthetic" translates roughly to "phat pheature".

I believe "critical aesthetic" means that a vocabulary has evolved with which to discuss a particular body of knowledge, usually from an artistic standpoint.

For example, there is a critical aesthetic for the discussion of Shakespeare and Hemingway and other writings, and a critical aesthetic for the discussion of film. It is the language of meaning used for representational comparison; and establishes the context in which the subject under study can be discussed.

To quote Richard Bartles, whose Designing Virtual Worlds devotes a whole chapter to the subject:
"A critical aesthetic is a system of ascribing meaning to individual examples of an art form. When formalized, it amounts to a theory for that art."

He actually makes an interesting argument for developing a more formalized approach to allow for more comparative discussions of virtual worlds (things beyond just, for example, "I think permadeath is the only realistic option for RPI muds").