I don't want to be called a smart ass, so I will say it's all according to what you are marketing
There are some areas of mainstream that could be considered over saturated...but that doesn't mean not to build for them, especially if you know what you are doing. Coming from adult, you have a good jump on the normal mainstream webmaster, most of them don't know how to build a decent site to begin with, let alone market it.
I don't think anything will be as easy as pre 2000, but who really wants it easy anyways. You lose your creative energies, and edge if it all comes to easy.