>Gen 1
+Introduced the most amount of pokemon until B/W
+Still pretty dificult by today's standards
+Simple, fullfiling story
-A lot of broken mechanics
-Could've been a better game if only they had more people developing for it

>Gen 2
+Continuation of previous game
+Kanto makes the game look a lot bigger
+Lots of sidequests and explorable areas
+Introduced many features without taking away any
-Least amount of new pokemon introduced
-No diversity in routes, half the good gen 2 pokes were caught post game or were weak
-Very difficult to get experience and wild pokemon were too underleveled even by trainer's standards

>Gen 3
+Great region and many places to explore
+3rd gen with the most amount of pokemon introduced
+Introduction of many new features and born of the meta
+Battle Frontier
-Removed a couple of good features
-A lot of the old pokemon were impossible to get or locked behind a shitton of work/games/gamecube bullshit
-Forgettable characters

>Gen 4
+Huge region to explore
+Great amount of post-game content
+Introduction of many features to polish the meta
+Introduction of wi.fi capabilities
-A lot of the routes slow you down
-No diversity in pokemon you could catch in main game (platinum helped with that)
-Way too many trade evolutions and legendaries

>Gen 5
+Most pokemon introduced in any gen
+Best spritework and arguably pokemon representation of any gen
+Most compelling story
+Added few but cool features
-Incredibly linear, half the map literally blocked out of laziness
-Had to transfer a lot of old pokemon until B2/W2