We haven't read a lot of them at our house because my kid wasn't a huge fan but I've been shelving Berenstain Bears books in libraries since 1983 and they are constantly being checked out.
Shelving these books is an easy task when they are just grouped together with books by authors starting with B or on the Berenstain Bears shelf. The library at my kid's school where I shelve now puts them first by author and then alphabetically by title. I'll leave you to imagine the chaos created on a daily basis by 5- to 9-year-olds searching for their favorites. I'll put them in order, boggled by the sheer number of books that begin The Berenstain Bears and the... That in itself isn't too bad but B is a popular letter for surnames of authors of kid's book series. This includes Clifford the Big Red Dog by Bridwell, Franklin the Turtle by Bourgeois, and the Arthur books by Brown. It takes forever to get to the Cs. So please, if you plan on writing a successful series of children's books, pick a pseudonym starting with J or Q.
Regardless of their critical acclaim and my own take on their appeal, I think it is worth noting that the Berenstains created characters that have remained appealing to children since the 1960s, a considerable length of time. The chronological list of their titles reveals a lot about changes in the way we've raised children over that time and what we've had to prepare them to deal with. It's also an interesting view of how publishing trends have changed, particularly with the increase in religious or inspirational material and publishing houses dedicated to those works. The Bears are probably a gold mine for sociologists and cultural anthropologists. It will be interesting to see where they go from here.