Well the number of people who would become serious musicians, never mind successful ones is pretty small to begin with, and I don't think that group has really changed in size due to the existance of music based games, I mean there are still plenty of "basement bands" hoping to make it big.
Not to mention the fact that even with such small numbers, I've actually been hoping for less musicians because I'm one of those critics who feels that rather than standing by developing band with ups and downs, right now there are simply so many that if a band falters they just replace them with something else. A very much "flavor of the week" kind of thing combined with ruthless profiteering and absolutly no loyalty to the talent. Basically if a band hits a rough spot, the industry won't be there for them, but if they get through it on their own and there is money to be made, well they will be the first knocking on the door.
There are exceptions to this behavior of course, but the bottom line is that I think less musicians would mean a return to older models and the industry standing by the talent it has rather than taking a plug and play attitude and disposing of any act they don't have an immediate use for, figuring they can always drag them out of the gutter and dust them off later if they really need them (which is typically unlikely to the eyes of many in the industry).
At any rate, Zepplin is timeless enough where they really don't have issues with popularity, but I think a lot of older music is getting attention because of these games (as others have said), rather than falling by the wayside.
Love him or hate him, but Meatloaf was exceptional in being able to do the "Cross Generational" thing with songs like "I Would Do Anything For Love, But I Wouldn't Do That" and "Rock and Roll Dreams Come Through". Right now I think Guitar Hero is providing a means for older acts to more easily do the same kind of thing with their older music. Not everyone scores big with new material the way Meatloaf did, and a chance to resurrect older stuff usually isn't bad.
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