>>48153887Sinnoh lets you catch the Lake Guardians before the Elite Four if I'm not mistaken. It also had Iron Island, Battle Zone, Route 212, Route 220-221 to Pal Park, and Route 224 from Victory Road to the Shaymin Gratitude Rock (leading to Seabreak Path in Platinum if you had Oak's Letter). Kanto had two alternate paths to Fuschia: Cycling Road or the maze south of Lavender. Similarly you can go from Fuschia to Cinnabar or Pallet to Cinnabar. Johto had Route 45 and 46 connecting Blackthorn to Route 29. Hoenn probably had the most optional routes and pathways. Routes 114, 115, 105, 106, 107, 108 (including the Abandoned Ship) 109, 134, 133, 132, Pacifidlog, 131, and 130 are all optional as far as I know.
