Most NFL QBs will never be top 5. Some can work well within a given system. Surround a particular type of guy around a particular system, with a lot of talent, they can be playmakers. Some can only be game managers.
I'd never consider Brad Johnson to be top 5, he doesn't have top 5 ability. He doesn't have the arm he once had, and it was never that strong. He's not very athletic at his age. But he is accurate, and doesn't make bad decisions. Only real flaw is that he holds onto the ball far too long (though he doesn't give up many sacks anymore), and doesn't take many shots downfield anymore. He'll just throw the ball away, and live to fight another day. So he's a good manager. In the right system, surrounded by top ,he's made some Pro Bowls, thrown some touchdowns, took some teams to playoffs, and won a lot of games. Don't give him protection, he can be average.
Drew Bledsoe is a playmaker. He's got a great gun. He's tall, and can see the field. He's very accurate. Give him time, and some good recievers to throw to, a runningback, and he can put 30 points on the board. He can, and has, taken a team to the big dance. Surrounded by the right talent for his abilities (not necesarily Tom Brady's abilities), he certainly looks like a top 5 QB again. Take away that talent, or the right talent for him, and he can look bad on a 4 and 12 team.
Both QBs have shown the need to have some talent around them. One has top 5 ability, one does not.
Top 5 this year.
1. Favre - OK. Maybe HE could have done more last week with the same talent. Assuming the coordinator isn't Henning.
2. McNabb - Becoming an accurate, strong armed pocket passer, with the feet to get outside and a running backs moves. Gets rid of the ball quickly. I remeber having McNabb/Culpepper debates with Collin. Yeah me.
3. Bledsoe- Think of our defense with their offense. Damn. I told yall Bledsoe would be strong this year.
4. Rich Gannon - Numbers don't lie. This is going to be his 4th straight big time, Pro Bowl season. Not a great arm, but a great QB. Accurate and gets rid of the ball quickly to great recviers.
5a Manning - On the road to 4 straight 4,000 yard seasons. Looks much better now that he doesn't have to score every time he touches the ball.
5(b) Aaron Brooks - Just needs to be consistent. His mechanics are a little sloppy, but he has all the tools McNabb does, and is patient in the pocket.
5(c) Garcia - A less consistent version of Gannon. Better athlete, but I don't think the Raiders would do as well with him.