Movies and TV shows get a nice budget, artists and effects to work with in depicting the future which often why the future can look so grand and epic in fictional depictions. Even now in a time when we should "know better" we can't help but depict even the fairly near future as just being spectacular, clean, with radical designs.
Unfortuantely, practicality, financial motivations, bureaucracy and sorts of other nonsense can put a damper on that real quick.
Forgetting more fantastic aspects of the future like flying cars there's really not much reason at all to think that the future is going to look too much different than it does today.
Sure, building materials are going to change, design styles and aesthetics are going to change Local politics and economics are going to impact how clean things look (mostly a function of the local crime-rate and where business is centered.) But overall things are going to look, well, the same.
I think Back to the Future depicts the distant future the best (again excluding the technological aspects.) The town square is not vastly futuristic looking, there aren't 200-story tall buildings standing grandly in the background and all of that it's still largely the same space.
Sure the parking-lot in front of the "courthouse" is now a pond, the building itself now a mall (presumably with underground parking or a nearby parking lot connected to the building via underground tunnels or something.) In 1985 we see that the town-square is a cesspool full of crime, Pay-Day Loan businesses, porn shops and theaters and pawn shops. In 2015 the town square now has a mall and thriving businesses, it's much cleaner and has a welcoming look.
We can infer the "politics" that happened between 1955 and 2015 on what happened, when the Twin (Lone) Pines Mall was built it took business out of the center of town and spread it out to the suburbs causing the town center to deteriorate as businesses moved to the mall. Likely this all stemmed from Mayor "Red" Thomas' tenure as mayor. Goldie Wilson's tenure as mayor must have reinvigorated the downtown area by making the old courthouse (or community center/half-way house as it was in 1985) into a mall which attracted businesses back to the center of town as well as clientèle and shoppers.
So the economic conditions of downtown Hill Valley improved over the intervening 30 years (possibly at the cost of the decline of the Hilldale suburb) but we can see that for the most part the area looks the same. Sure design styles and color have changed but, mostly, the place is the same.
Which is most realistic. Right now as I think about areas around me and how much they've changed since I left high school 15 years ago other than some expansion into undeveloped areas, the tearing down of a building or two and the erection of another the area is pretty much the same. Dowtown? Other than the development of an entertainment district and a new arena it's largely the same as it has been my entire life.
The most realistic look for the future is pretty much for it to look the same. Different colors, cleaner or dirtier depending on which way you think the local crime-rate/economy went but mostly, the same.
Hell, out there there's a series of pictures of an area and how it looked over the course of decades and other than some architectural changes improvements to buildings, the expansion of roads to allow for more cars and parking, it looks the same.
The future is boring and it's always going to be boring.