>>54202757Expanding on this a bit:
I think the first and second generations of Pokemon have the best world design - there are multiple paths a player can take to progress to their next goal, each with their own sets of obstacles and challenges. Moreover, it does feel like a more realized, believable world (urban japan vs rural japan) - though it helps that they actually are based on real-world locations.
The third generation feels a bit more video game-y; while it's fun to explore, the game's levels are a mishmash of biomes that aren't really congruent to each other. A believable world wouldn't have a volcano, a jungle, a desert, and an ice cave (?) all within a mile of each other.
The fourth generation does feel like a bit more of a return to a believable world - though the player can no longer choose between progression path and is often roadblocked for contrived reasons. While the world itself is believable, interacting with it reminds you that you're playing a video game and can't get too immersed.
From the fifth generation onward, the biome mishmash of the third generation and the linearity of the fourth generation are both drastically increased; I do not believe Pokemon has good world design from this point onward.
Pokemon's level design is more or less consistent in quality from the first generation through the fifth generation, though starting in the sixth generation it seems to become extremely simplified/infrequent and by the eighth generation it's gone entirely. This is almost certainly due to the series' shift to 3D; 3D level is obviously drastically more difficult than 2D and it's pretty clear that Pokemon lacks the talent, or perhaps willingness, to learn it.