Ovy is on the mark about all of the predictions....Very few are close or right.
PS3:
Predictions are far too high. 20-20.5m is a good middle ground for PS3 numbers. It's a better number than most fan predictions at the end of 2007 (which put the PS3 around 16-18m in typical predictions, and 20m at the highest end).
Grade: C- (far too high given the low PS3 userbase)
X360:
Too low. Many, many users have argued 22m-24m for the entire year. User predictions have stayed steady with the X360 at said level. I was the only person bullish enough to go above 25m with a 27m prediction made last year. I know I'm too high, but the X360 looks to land anywhere from 25m-27m.
Grade: B- (closer than PS3 estimates, but still pretty low).
Wii:
Too varied. On one hand, you had a lot of people (including myself) going too low -- Into the 35m area late last year, which was off pretty bad (the Wii, at a minimum, is tracking at 38m, but could go as high as 44m, with 40-41m being a great median), but then you had guys like JL predicting 60m, and securing a bandwagon of supporters that were above 50m which was just insanely stupid too. However, predictions have got better over time to more reasonable levels.
Grade: B+ (considering recent predictions are in the 40m area, which are very reasonable).
Obviously, you can see my own predictions and how bad they were/are from late 2007. However, it was/is fun that I made them before most people did.
Back from the dead, I'm afraid.