The Watt vs. Houston question is interesting, even if being named first team All Pro is not exactly a "rat's ****".
Discounting Watt's offensive gimmicks, their headline numbers are pretty similar.
Watt: 78 tackles, 20.5 sacks, 4 tackles for loss, 10 passes defended, 4 forced fumbles, 1 blocked kick, 1 INT (pick 6)
Houston: 68 tackles, 22.0 sacks, 6 tackles for loss, 5 passes defended, 4 forced fumbles, 0 blocked kicks, 0 INT
So why does everybody's eye test put Watt in a class by himself?
Here's an indicator: According to PFF, Watt logged an astounding 54 QB hits to Houston's 8. While "hurries" should rightfully be viewed with skepticism as to their impact (Watt 54 vs. Houston 56 according to PFF), the value of QB hits should not be in dispute.
Those Watt hits amount to a disruptive affect on nearly 10% of the opponents pass plays, a truly remarkable figure. That makes for a wide margin over Houston.