@Phoenix1983 That's impressive and enviable.
Two questions, if you don't mind:
1. What was your favorite match that you ever watched at the O2? Players and year.
2. Who was the player you thought performed at the most insanely high level? IOW, who was the greatest player you saw play there.
1. Tough call between the 2016 and 2017 finals. I was very pleased that Murray captured the title (and YE No 1 ranking) in a straight shoot-out with Novak Djokovic in 2016. However, the Dimitrov-Goffin final in 2017 was an unexpectedly entertaining and high-quality match, given the relative 'lowliness' of the names involved.
2. Zverev's 2018 final performance was the single best that I saw.
Also, I know you didn't ask, but the worst match I saw was the first I attended, namely the 2011 round robin match between Ferrer and Novak Djokovic. Ferrer won easily against an opponent who was clearly exhausted from his remarkable year.
Full list of matches I saw:
2011 RR: Ferrer - Djokovic
2013 RR: Djokovic - Gasquet
2014 RR: Wawrinka - Cilic
2016 F: Murray - Djokovic
2017 F: Dimitrov - Goffin
2018 F: Zverev - Djokovic