Well, the site probably shouldn't estimate sales based on absolutely nothing, put out a press release trumpeting that number without even calling it an estimate, change the number as real data comes in, and then tell some random reporter the whole thing. That's a big, embarrassing sequence of dumbness.
But as a responce to botching MGS4, it should be pointed out that VGC nailed Mario Kart Wii launch numbers in America, and then was the first source to predict Wii Fit sales under 1M for launch month in America. VGC was talking about how incredible the MKWii launch was and how the Wii Fit launch missed its goal before anyone else.
Also, the site should start talking up its community and the speed with which it gets numbers instead of its accuracy. Don't try to take on other sources in terms of accuracy, as it will take years to get to the accuracy of benchmark sources. The instant analysis performed by the community, as well as having the only numbers to go by for several days, or several weeks in America's case, plus the huge database of publicly available info, represent different values that the other sources can't compete with VGC over.
There will be people, like Gamasutra, which put a higher demand on accuracy in areas where VGC doesn't have it yet, and that's not the problem of those people. But don't let them reach a total conclusion about the site without getting a mention for the speed of the numbers, the scope of the database, or the quality of the instant analysis provided by the community.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
