>>432018488/10, overrated but still overrated for a reason, it's a really good route
>>432018795/10, I really like all the encounters, and it has personality, but it lacks exploration, way too short honestly even for a simple route, but serviceable.
>>432019749/10 amazing trainer battles on this route in both bw and bw2 and plenty of exploration to be rewarded with, interesting reasons to back track too, longest route in unova I think
>>432019777/10, amazing top tier exploration, but it makes very little use of all that space, could have so much more.
>>4320199110/10 literally has everything, amazing trainer battles with a good balance of double and singles (Platinum was great about that) really tight design, makes maximum use of space with narrow paths that weave in and out of one another, and it's layered really well. top tier music too.
>>432020198/10, beautiful music and really well designed in both aesthetic and layout. A little short but that's ok, solid overall but not perfect really.
As for myself I'd say route 4 unova, I've heard it's not very popular but honestly I love it's lay out and think it pulls of the desert theme the best out of every desert area. The music is good, I like the pokemon and theirs plenty of trainers, But what really cements it is how it changes. In bw it's clearly a construction site where they're trying to expand the city, connecting castelia and nimbasa. In black 2 you see this plan finished 2 years later, and in white 2 you see that it was canceled due to the discovery of ruins. The fact that it changes at all shows that they thought through the implications of a time skip, but the fact that the outcome differs between versions is above and beyond. As over used as the term is this OOZES soul and this is the type of world building we need more of in pokemon. Sry for the paragraph.