NWO 08 by far. Every other match is average at best or not that good at all. Both the summerslam matches SUCKED, The ironman is average, and the I quit has its good and bad parts.... Both HIAC matches were just meh.
The Iron Man match was very gimmicky, so I don't really compare it with Angle/Brock or HHH/Rock. On its own terms, the Orton/Cena iron man match was actually well done and they found plenty of ways to fill up that hour with interesting storytelling to where it was just a fun ride.