>First two towns are completely garbage and forgettable with no reason to ever go back to either of them
Gen I had the Tangela grass, the alternate path to Cinnabar, the 8th gym, and the path to Victory Road
Gen II had bank of mom, path to KANTOOOOOOOOOOO, all the stuff you got from the lab for hatching Togepi and other stuff, and the Mystic Water guy
Gen III had the Amulet Coin and a Johto starter
Gen IV had an Odd Keystone, Lake Verity, Splash Plate, X-Scissor and Pal Park
Gen V had False Swipe, Protect, Hidden Power, Super Rod, Bianca rematch, Toxic, Waterfall, Double Team, and Larvesta egg
Gen V.2 had Energy Ball, Water Stone, Expert Belt, Benga's shiny, the Alder fight, and Pledge Grove for Keldeo
Even Gen VII has reason to go back home, with the Mind and Earth Plate hidden outside after beating Nanu, and to Iki town for the Zygarde core.