His best time was actually post TNA/Pre NJPW in the 2010s with some NJPW bullet Club crossover if I remember right. Prior to that he was more like just a guest from TNA as Hoss said
I hate to be this guy, but AJ was huge for ROH in the first 4 years of the company. Once the RF shit happened, TNA pulled any conracted talent from taking ROH dates. Had that not happened he was the first ever Pure champion and was working almost every ROH date up until the pull from events. Also was what the second tag champion with Red. His feuds with Paul London and Jimmy Rave (which funny enough occurred after the ban from ROH) were great and then a list of great matches was right on par with any of those early guys like Daniels, Low-Ki, Joe, Bryan. I mean hell Dragon was hardly around from late 02-05 with ZERO-1 and NJPW dates taking precedent for him.
I'm like the biggest ROH 2002-2006 simp, maybe have rewatched it like over 5 times over the past 15 years and AJ was absolutely a force early on and I'd put him on a rung below that Daniels, Dragon, Punk, Joe tier. But to say he was a guest is insane.
For Reference:
February 2002 to April of 2004 (when TNA restricted talent)
# of ROH Dates:
Aj Styles: 29
Christopher Daniels: 29
Low-Ki: 18
American Dragon: 16
EDIT: I also now realize I am arguing on the side of "I Wonder", I can assure you these things can be mutually exclusive to each other,