Dances With Wolves is at the absolute top of my Overrated list. Made just before Kevin Costner was exposed for the second rate talent he is by the movie Waterworld, I found the movie to be horribly paced, which led to it being about twice as long as it needed to be. And, oh, look! Here's a white woman for you to fall in love with out in the middle of nowhere! Just painful.
Not a blockbuster, but a way overrated movie in my book - Body Heat. Supposedly a stylish thriller, I found it to be predictable and indistinguished. That would have made it just bland, but then it included a few scenes that just made me want to turn it off (something I almost NEVER do with a movie, no matter how bad). Kathleen Turner tempts William Hurt at the bar, but leaves without him. He follows her home. She rejects him at the door. He's about to leave when, suddenly, passion just overtakes him, he breaks through the window by the front door and throws himself at her. Of course, this works out as they proceed to, well, you know. I'm sitting there imagining how the scene would have played out if it had been me and it had been real, what with the police hauling me off and all.
I'm not sure it's Top 5 material, but I'll throw out Rocky, if only because it gave us decades of additional Sly Stallone movies.