>>58221772Route 19
Route 20
Route 21
Route 40
Route 41
This was the most interesting water route before Hoenn and the water is the least interesting part about it, the actual islands are interesting. The water routes themselves are not interesting. People bring up the Abandoned Ship, and yes, that's interesting, but it's the part of the water route that isn't water. I haven't even mentioned that you listen to the same surfing theme across every single water route. It's not like land routes where your route music updates. For the bits of water routes that take place on land, the music is just reused.
The two snow routes are really cool. New music (a day theme and a night theme), Hail weather conditions, Ice-type Pokémon that you haven't seen before (Sneasel, Snover, Snorunt, Delibird post-game), snowstorms blanketing your vision, trudging through the snow and the wide open field while being ambushed by Trainers. You find a cabin for respite in the storm. Pokémon had never done a snow route before that and they nailed it, and it doesn't overstay its welcome. It's part of Snowpoint City, and you see more snow as you ascend Mt. Coronet.
Other than that, Sinnoh barely had water routes to begin with, and most of them were one and done. The surfing speed boost in Platinum is overpraised, I can see it applying to Hoenn which has seemingly endless water, but not a single person has ever said "too much water" in the context of Sinnoh.