>Gen III
Started the trend of taking away more features than giving. Is the first to invent a regional dex where the full Pokemon lineup isn't listed. Asinine trading mechanics, especially with FRLG and Emerald. Plot focuses more on legendaries, and Brendan and Wally are much friendlier than Blue and Silver. FRLG also removes features RS had, a trend that will also continue in HGSS and ORAS.
>Gen IV
Started the trend of removing content, only to specifically add it back for the third version, as seen with DP removing the Battle Frontier, only to bring it back for Platinum. HMs became a major exploration element, even more than Gen III's.
>Gen V
Region progression has become even more linear than before, with more NPC and item roadblocks existing to prevent you from exploring certain areas. An obvious example is all of the past locations in BW2, which are roadblocked as they have no relevance to the plot, whereas in previous gen games like RS, Pacifidlog is accessible even before beating Gym 7. Gym Leaders have teams that peak at 3 mons. Games become much more plot-oriented, and players are forced into tutorials a lot of the time, like with BW's musicals and BW2's Pokestars. BW2's backpedaling on BW's all-new American region was the start of constant Gen I references in an attempt to appease those upset by BW.
>Gen VI
Insistence on adding new gimmicks to try to keep the metagame from stagnating. Exp. Share being reworked and given out in the maingame makes it too easy to accidentally overlevel. Few new Pokemon. Removal of minor gameplay mode, Launcher.
>Gen VII
Lack of polish, for lack of a better term. Roadblocks are the same as Gen V and VI's, however, the constant camera pans and black screens make these look messier than ever before. Removal of major gameplay modes, Triple and Rotation battles. Multiplayer connectivity has gotten worse, when in every other gen it has gotten better and better.
