I think rating the mentioned book series, if being overrated or not, is a bit hard, because most of them being rather niche-products. So they are developed to please a very certain range of customers.
The twiligth series, hunger games series and Harry Potter series, were made with the purpose of "youth books". So the writer had in mind, that he wanted to please a certain peer group of yet non adults. That they dont have an intense plot, may be quiet extreme when it comes to black and white thinking, is normally, thats what they are supposed to be. Out of that I think the Harry Potter series is for adult readers the most pleasant one. At least for me, it rather bores me to read about typical teenage love issues for 50% of the book, and because of the Potter series starting before that age, thank god it avoids that stuff mostly. XD But blaming youth books, for having attributes that are typical for youth books, simply becauses it pleases the peer group, that these books are made for, is a bit weird I think. ^^
Same goes for "50 Shades of Grey". It was not written with the purpose of getting the "Pulitzer-price" for Bellestrik, but in the intense of pleasing a certain audience that wants to read an erotic book, with that. And additional to get some publicity, so that it sells better. ^^ In the end, I did not understand what all of that attention and publicity was about, so that typical love romans exists since decades, and I remember that in the "Al Bundy" series, Peggy Bundy was mentioned several times to read similar "romantic books", so they must have existed in the US area as well. So I really did not understand all that excitement about the existence of such books.
When it comes to "Lord of the Rings", then it hardly can be compared to the ones before. Its an good written book for adults, being in an fantasy setting. There might be in general some better books, but among the fantasy-books its one of the best series existing, due to plot, character design and development... You have black, you have white, you have grey; you have different set of plots to bring variety to the reader but that are as well linked to each other; the plot lines follows classic drama style, ... The writing style is more complicated then the books mentioned before, but in opposition to the above mentioned series, it was not written with the focus of teenagers or sexually bored housewifes, but to interest people with an interest and experience of reading.
Just like I find it weird to blame youth books for their rather mundane plots and characters, I think its weird to blame a book for being focused on readers that are on purpose interested in a more complicated story plot and more matured character styles.
Out of personal interest I´d say Twilight, Hunger Games and 50 Shades to be boring, because the two first mentioned have too much teenie romance plot in it, which bores me and the last one might be embarassing for house wifes, but if you dont get excited about two grown ups, doing in agreement stuff that sexually pleases them, its as well rather boring. XD
Harry Potter I liked because at least it focuses more on a plot, while being more of "easy reading", while Lord of the Rings is quiet the same, but for an more experienced audience. What I miss in Lord of the Rings is more balance to the female actors in it, but it was written about 1940 I think, so from that point of view its ok. ^^