Technically every QB is a "system" QB. I would say that Manning is very lucky because unlike most QB's in the NFL, he hasn't had to deal with change. In Manning's 11 year career, even though their have been changes to the head coaching position, they have never changed any of the offensive coaches during that time and he has always been surrounded by Pro Bowl talent. Not having to deal with any change to the offensive coaching staff whatsoever has also helped him to call his own plays, something that other QB's like Favre, Brady, Brees, or Warner would be able to do if they too played under the same staff and system for 11 years. I'm not trying to say that Manning is a bad QB, but tell me one QB that has had the luxury of playing for only one offensive coaching staff and has never been surrounded by average or questionable talent on the offensive side of the football.