>>37281093Kanto. You can do some things around Misty in different orders, and after getting Cut you can do the next 75% of the game in almost any order you want.
Johto has a very deliberate split halfway through the game that you can do in either order, but it's linear outside that third of the game. It does have more extra areas in older places you can backtrack to than Kanto did, which became a standard in all the later games regardless of how linear the main plot becomes.
Hoenn and Sinnoh are both linear, you can only maybe only put off a single gym for a while if you walk past it (and even that's not true in ORAS). The overall region maps obuscate that though, they have a lot of crossroads and extra routes that make it hard to predict how you'll have to go through the region, which is why people remember them as more non-linear than they actually were.
BW1 Unova is totally linear and have a rather simple region map that makes that more obvious than Hoenn and Sinnoh. The individual area maps have effort put into them though, with a lot of side areas. BW2 Unova and Kalos are the same, but the region designs are now less obiviously linear again. The individual place maps aren't as good in Kalos though.
Alola is totally linear, completely obvious about it because of the bottom screen showing where the next event flag is, the island setup makes predicting how you'll travel around easy to predict, and the individual maps contain a lot of hallway-like designs.
