OS: Misty in generell, Kanto gym battles, plot, actual development for both characters and pokemon, Kanto Pokemon overshadowing Johto pokemon, pacing, for today's standard super shitty battles and much more.
AG: May's Hoenn contest and development until the last contest, Ash not having any rivals, TA/TM climax not being as epic as in the games, Max not having many centric episodes, Brock doing nothing
DP: Dawn's whole team in generell was underdeveloped with Piplup being an annoying screenhugger, Paul's team against Ash in the league, too many episodes for a badge quest, pacing being **** in many parts, TG build up was as unimportant to the plot as in the games, Aimpom and it's release being the most pointless release ever, Togekiss
BW: Iris in generell and her goal being more underdeveloped than Misty, Ash's pokemon team being weak with many forgettable pokemon, less development for the whole cast, only a couple of episodes for the rivals, Dawn being pointless, Charizard's return in generell, Dragonite, not taking the TP plot (neither BW or BW2) for the anime, dissapointing battles after DP, the league and the badge quest being rushed as hell
XY: Serena showcase and her crush, league somehow, only a couple episodes for the rivals, TR returning to their old form, Noivern, Korrina arc being a bit pointless, continuity, Luxray, Sawyer's progress in such a short time, Ash being too much of a Gary Stu