This one is pretty damn tough. He's never been that well known despite having an impressive resume of titles.
I found the person! All it takes is google and the hints. I have NO idea why he is the most important. I never even heard of him! Trust google young padawans. Tis your friend.
Edit: think of worked for bioware now working for en masse.
Indeed. First search and I found this dude as well.
I call complete bullshit on this particular quest, however, since this guy is NOT important at all and nothing supports the claim that he is. I think the guys at GiantBomb just arbitrarily picked some unknown guy and labeled him "most important" in an ironic twist to throw off virtually everyone that undertakes this quest. I can think of far more important people in the long history of video games than who this person turned out to be.