As with any league, a lot of this is dependent on what type of scoring system you use. Some leagues award more points for TDs, other more points for yards, or completions, etc. Most leagues are a little bit different, so you have to tailor your strategy to the point strategy of your league. But hopefully you know that already.
The way I see it, there are really 4 Quarterbacks that stand out above the rest, fantasy wise. They are Peyton Manning, Carson Palmer, Drew Brees, and Marc Bulger. You could make an argument for Tom Brady (especially with the extra weapons the Pats have this year) or maybe Donovan McNabb, but in my mind those 4 are the best fantasy QBs heading into the year.
First, Peyton Manning. He is the model of reliability. For one thing, he has never missed a game in his NFL career. That's helpful. But he always throws for a lot of yards, throws a lot of TDs, and has a good completion percentage. He probably won't match the 2004 numbers ever again, but he's a good bet for around 30 TDs and somewhere around 4000 yards.
Next is Carson Palmer, who is might be the most talented QB physically. He has a rocket arm and is very accurate. He was 5th in the NFL in passing yards last year, has a good completion %, and was top 5 in the NFL in YPA. Also, he continues to have great weapons outside with Chad Johnson and TJ Houshmanzadeh.
The guy that emerged last year was Drew Brees, who thrived under Sean Payton. He led the NFL in passing yards last year while throwing 28 TDs and completing 64% of his passes. And with the news that the injury to LT Jammal Brown is not serious, there is no reason to think he can't repeat those numbers again. The talent at the skill positions is superb and Sean Payton is one of the top offensive minds in the NFL.
Last is Marc Bulger, who I think should explode even more this year. He was 3rd in the NFL in passing yards last year, and he finished with a 3:1 TD:INT ratio. Also, like Brees, he is working for a great offensive coach in Scott Linehan. As long as Bulger has been healthy, he's been a consistent 4000+ yard passer.
But how to rank them? I would probably go like this (again, depending a lot on what type of scoring system you use):
1. Peyton Manning
2. Carson Palmer
3. Marc Bulger
4. Drew Brees
How would you rank them?