I really like Montpellier, but just like with Paris (on a much, much smaller scale of course), the center is really nice, but not so much for the rest of the city.

I think that's the case with most French cities. Nice centers but the surroundings are average at best. An exception would be Marseille, it is filthy even in the center ;).

Yeah that's pretty much the design of French cities (and maybe European cities to an extent). The center is great, around the center is meh, suburbs are to be avoided. Very different from the typical American city.