@elliott I'm sure other folk will do the heavy work of doing the year by year cases but instead of giving you a list right now of why he was a BITW candidate I'll give you a list of years were I think he wasn't, just so you can get more grounded expectations.
2014: 4 months of work before out with injury, enough good and great stuff to at least say "if his neck didn't give out, he could've have a case".
2015: Basically 3 months of work before he had to retire due to concussions. He still had good matches with the likes of Luke Harper and even Seth Rollins and Dolph Ziggler but his year never really get going to even try to hypothesize like with 2014.
2016: retired
2017: retired:
Also, 2001 he might not be "best in the world" but for sure it's a year that makes his case stronger as he's a damn rookie and is putting out classics already. So that year shouldn't be dismissed or skipped if anyone wants to do a deep dive on his work.
I'm actually kinda interested in a case for 2003. There's the London match and he still puts other good matches in ROH but he barely works there (5 matches) so if he has an argument, it would be because of his New Japan (were it's basically a bunch of tag matches) and England runs. How much of that do we have available on tape?
While we are in a year by year breakdown, 2009 and 2010 are also interesting years to me. I felt he had become kind of stale in 09' as a singles performer in ROH, but signing with WWE meant he had that farewell tour in ROH that turned it around for him. His case is mainly done in other promotions though, like his appearances in Chikara, PWG, AAW and wxW.
2010 is a prime example of his versatility, imo. Not only is he able to stand out in WWE despite being presented as a loser and a geek/nerd on TV but him getting "kinda fired" (that's such a curious time) leads to a short and awesome indy run with him working a fuck ton of places and doing EVOLVE, AMBITION and DGUSA were he does shit he wasn't doing in WWE to great results.