Alterego's quote has the right idea. Obviously a product being a commercial success doesn't inherently give it value, or make it good, yet at the same time it must be doing something right to attract so much interest from the public. And it really is just about the only objective way to measure success that we have. You might look at me funny if I insist that Superman 64 is the greatest game of all time, but ultimately that's my opinion, and any attempts to disagree really are subjective in nature, thus unproovable.
I also believe that people are not idiots, and have a good idea of what they want. You will hear a lot of people condemn anything that becomes popular as faddish or part of a herd mentality, but I think that's being too cynical, and giving folks too little credit. Especially since most peope who say such things are inherent elitists who believe they should be the arbiter of quality for everyone else. 
End of 2008 totals: Wii 42m, 360 24m, PS3 18.5m (made Jan. 4, 2008)
