Yeah ive heard PES2017 and 19 had the best ai overall. I guess its all subjective - all this "which pes has/had the best AI?". Even if this is true, (for me ) they just dont have what pes2021 has as a total package. I think overall, PES 2021 has the most good collectively (when looking at the entire package, graphics, animations, variations, ball physics, ai..etc), which is why its my one and only played football game currently. I know 19 was supposedly one of the most superior looking games in terms of lighting (ive heard this somewhere recently), but i definitely couldnt go back to playing 17. Looked at some of my uploaded pes20217 videos and it looks rubbish in comparison.
Anyways, we are all looking for different things i guess.. but if i had to choose only one football game to play for the next 5 or so years, itd still be Pes2021 - with the ongoing modding that's really built this game into something else. I do wish or hope, that one day someone can really work on modding the player positioning (compacting the middle of the park), and ai, to a point it leans way further to the realistic side.
Speaking of ai, and gameplay etc. ..I am convinced we are all playing a different pes2021 lol... meaning we are all using different settings, patches etc.. im on vanilla exe, but using evoweb patch + klashman tactics (both having some effect on edit file and team settings/tactics), and probably one of the biggest factors is my own style of play... here is my version of Newcastle vs Arsenal:
a few bad decisions defensively, player positioning wise.. but not much lumping it forward. I think this also has a lot to do with the way one defends .. ie. calling 2nd player in .. and anticipating passing lanes... There were a few long shots from ai which was nice. Only played one half