I'm surprised that I absolutely forgot to mention some other things that are overrated. They might not be too popular now, but they were before.
Let's start with…
Super Smash Bros. Brawl - When this game came out, everyone was talking about it, mentioning how awesome this game was. I can understand that there's a lot of variety and modes that makes the game appealing and of course, I was one of those people who were amazed by Brawl. Although when you played it for a long time, it kind of loses it fun because it's just like the other Super Smash Bros game in previous Nintendo consoles, but with more things, pretty visuals and you use a Wii controller (although you can use other controller types like the Gamecube controller to play this game, but if you don't have one, you have to stick to the Wii remote).
the Lord of the Rings trilogy movies - It looks stunning, epic and filled with cool characters, but I find the movies wayyyy too long. Sure the producers and directors of the films were doing their best to fit as much story as they can to make a trilogy out of this series, but long movies certainly aren't my cup of tea.
Nirvana - I hope I don't get any glares from anyone, but I find them overrated. I understand the lead singer Kurt Cobain was a legend in grudge rock in the early 90's and his death shocked so many of his fans, but I feel like Nirvana's music feels more like a trend than an inspirational band. Unless if you have grew up listening to this band, in my opinion, that would be more consider as inspirational rather than being a follower, like some of the fans are… or were.
Johnny Depp - I think he's a good actor, but I think people (such as many fan girls) are too crazy with his appearances in films or anything in general, especially in the Pirates of the Caribbean films or anything directed by Tim Burton, which by the way Pirates and Tim Burton are pretty overrated too.