I don't think we can know whether or not this is the case in our own lifetimes, because we are so immersed in popular culture that we can't be objective about it. Enough of our historical great composers weren't venerated until after their deaths, and to describe composers as "hiding" within the most popular media of our era is a great disservice to the many composers that don't have the fame, connections and reputation to be hired to write for these.

I would also point out that composing for a medium like a game or a movie places a great deal of constraints upon the composer, in terms of theme, cost of instrumentation, duration and most importantly: what is safe and palatable for an executive to approve of.