Respectfully, I flat-out disagree with this.
There are only 12 notes in the western chromatic scale, for instance, and yet we keep making new and inventive music with those notes. By that same measure, there are literally hundreds, even thousands of parameters on some of the synths mentioned in this thread; the sonic possibilities, combinations, and variations of which are virtually endless. And that’s before you apply said sounds to said notes.
Now, that doesn’t mean that the average synth user is going to break new ground every day; but then, neither do writers and composers. Quite the opposite in fact. The truth is that most people are content to copy what they’ve already heard, even when they aspire to invent something of their own, despite the otherwise inspiring tools at hand. That’s just humanity for you. Not that there’s anything wrong with that. I mean, we like what we like, and there’s not always a reason to reinvent the wheel per se. Hell, often that just leads to pretentious noise anyway.
However, in the hands of the truly gifted (and that is far fewer people than some of us would like to believe), any one of the more capable synths mentioned above (i.e. Peak, Hydrasynth, Blofeld, Iridium, pick your flagship soft-synth, etc.) could easily deliver compelling new sounds for several consecutive lifetimes. Frankly, the notion that “it’s all been done” is preposterous, and often just serves as an excuse or rationalization for the things we can’t do or don’t have, like talent, vision, or the latest premium gear. 
Cheers!