I remember seeing photos of the "Bitmap Brothers" team, they made that flashy new 3d speedball game, there were young guys, but there were also old guys in all the photos... I wonder how good these old guys actually are. :) Maybe its important to have young heads and old heads there, because they both have advantages.
The young guys are highly intelligent, and the old guys are wise. The old guys grew up in a different era remember, they were making all the monochrome vector games! hehe
But in say 30 years from now, the old guys grew up making the games we do now, so it will definitely be different.

Thinking back at it, in the Bethesda's video making of Oblivion (The Elder Scrolls IV) there was a proeminent figure that seemed relatively aged. I'm not sure what job he occupied, but he seemed quite involved in the process...

And then again, there's Warren Spector. He's not exactly old yet, but meh...
Sid Meier too.

The fact they started in the business at younger age may explain why they became legends, but it doesn't prevent older people to jump aboard. Dedication has no age.