Judge is INSAIN

• The best duo last year in man coverage was Charles Woodson and Al Harris of the Packers. There was no other pair of defenders who played so much man coverage that consistently excelled. Most of the other top zone defenses played at least some zone, but not Green Bay. But that's not to say they weren't vulnerable in the right conditions, as Plaxico Burress and the Giants showed in the playoffs.
• If you want "most successful" CBs, I think you need to look at opposing WR production.  And if you're looking for the top duo in terms of shutting down the top 2 WRs from the opposing team, you could look at  the stats from www.footballoutsiders.com/stats/teamdef.php. By the numbers the crown there has to go to the Chargers who were #7 in the league last year at shutting down the oppositions #1 receiver (generally covered later in the year by Antonio Cromartie, earlier by Drayton Florence), and #1 in the league (by a WIDE margin) at shutting down the #2 receivers they faced (generally covered by the maligned Quentin Jammer).
  
  • As an aside, if you're wondering why San Diego drafted CB Antoine Cason in the first round based on this you need to look no further then what "other WR"s did to the Chargers, which wasn't pretty resulting in a 30th rank in that category.
• Disrespecting the Raiders defense is something that lots of teams do, but the proof was in the pudding last year in terms of success against WRs. On the same Football Outsiders stat table you can find Nnamdi Asomugha's effect - which makes the Raider #1 against top receivers (again by a relatively wide margin), and #32 against second receivers....  so it wasn't just the run defense that needed fixing.
• And finally, for proof that the best pass defense is a good agressive defensive line you need to look no further then the Tennesse Titans, who were the best pass defense in the league according to the Football Outsiders stats (which are based on more then just passing yards per game) without a particularly dominant CB. For a team that was just average against #1 receivers, ok against #2s and dominant against everyone else something had to have been going right....

fenolitto, you are giving Hall WAY too much credit.  He is fast, that's a given, but his coverage skills are not the best and I'll take a big,strong receiver against him any day.  Nextly, coverage doesn't count for anything if you can't pressure the QB.  If the QB has all day, eventually coverage will break down. 

Overall, the Packers have the best pair of cornerbacks (Woodson should've been in the pro bowl last year over Harris at least, DEFINITELY over Terrence Newman)

Pacman will be re-instated and will help the Cowboys' secondary A LOT!

Cromartie had a good year last  year, and barring injuries, I think he will perform even better this year. 

Not the biggest Dre Bly fan but Champ Bailey is the truth.

As an overall unit tho, after the Packers I'd say next up is the Eagles.  Brown and Sheppard were both very good and the eagles have only gotten better with the addition of Asante Samuel.