This from SI.Com:
"He is possibly the worst overall first pick in league history."
For the record, through his first 16 games he had the third highest passer rating for any QB taken first overall--and it wasn't like he was in a great situation. 
For the record, Alex Smith was also drafted first. As was Tim Couch. As was David Carr. As was Ki-Jana Carter. As was Jeff George. As was Aundray Bruce. Of those players, he will certainly be better than all but Jeff George, and he will very likely be better than him.
For the record Jim Plunkett was drafted 1st by the New England Patriots in 1971. After playing there and for the 49ers, he came to the Raiders when no one else wanted him in the late '70s. When an injury forced Plunkett into the starting line-up for a 2-3 Raider team going nowhere in 1980, he led them to the Super Bowl, where he was the MVP. He won the Super Bowl again in 1983, and his Raider-led teams were consistently in the playoffs. 
Nine years after being taken first overall, Plunkett flourished. But after one season and two games of starting the jury is already in on the broadly perceived to be dumb, lazy, fat, physically gifted, fur-wearing black guy from the South who the Raiders drafted.
JaMarcus's passer rating for his last 7 games of 2008: 
88.4 149.1 51.5 42.0 85.7 128.1 98.9
Average Rating: 91. 9
It's ridiculous to say that he's the worst pick ever. The guy has had two shitty games to open this season. He's playing with two rookie receivers and his favorite receiver is out. He's led two touchdown drives in the final three minutes to put his team ahead. But the perception is that in every game he has ever played he has been absolutely awful. 
Why is that?
Look, I'm not sure how JaMarcus Russell will turn out. I hope he returns to end-of-last-season form today against the Broncos. 
But the excessive criticism of the guy has gone so far off the rails on a national level that it's become completely unbelievable.  It's hard not to think it has a little to do with race and a little to do with an "anything the Raiders do has to be a disaster" mentality.