17. Iron Man 2 - Average Score: 65
Tony Stark underwent deeper, personal changes in his second superhero outing. Iron Man 2 (directed by Jon Favreau) was, in many ways, bigger than its predecessor, but that's not always what fans or critics look for in a sequel. That much is evident from the critical reception of this film. It holds a critic score of 73% on Rotten Tomatoes and a Metacritic score of 57.
Reviews for Iron Man 2 were mixed. Some critics, such as Kirk Honeycutt of The Hollywood Reporter wrote "everything fun and terrific about Iron Man, a mere two years ago, has vanished with its sequel." Others such as Roger Ebert described it as a "not as good as the original, but building once again on a quirky performance by Robert Downey Jr." If nothing else, it's a testament to how vital Robert Downey Jr. was to the establishment of Marvel's entire franchise.
Iron Man 2 currently holds an audience score of 72% on Rotten Tomatoes.
16. Thor - Average Score: 67
Thor (directed by Kenneth Branagh) introduced the Norse god of thunder and his entire mythological world while trying to make it blend with the rest of the MCU which, up until that point, had been relatively grounded in a more traditional sci-fi reality. Thor brought with it an element of fantasy, but while the film may have received less than stellar reviews, that's not to say some critics didn't enjoy it, at least in part. The film holds as critic score of 77% on Rotten Tomatoes and a Metacritic score of 57.
Owen Gleiberman of Entertainment Weekly, for example, stated simply that "it's not art, but it's mighty fun." Other reviews were a bit more scathing. A.O Scott of The New York Times described it and its financial success as a "triumph of commercial calculation over imagination." One thing most critics agreed on was the talent of the film's cast -- Chris Hemsworth and Tom Hiddleston in particular, both of whom would go on to feature prominently in future MCU films.
Thor currently holds an audience score of 76% on Rotten Tomatoes.
15. Avengers: Age of Ultron - Average Score: 70.5
While it's no secret that the Avengers sequel was not as well received as its predecessor, Avengers: Age of Ultron (directed by Joss Whedon) was arguably more impactful in the grand scheme of the MCU, with its climactic end setting the stage for films such as Captain America: Civil War. Critics cited its antagonist, Ultron, as one of its major flaws. The film currently hold a critic score of 75% on Rotten Tomatoes with a Metacritic score of 66.
Some critics praised Avengers: Age of Ultron as a "surprisingly touching and even romantic adventure with one kinetic thrill after another," as Richard Roeper wrote in his review. Other critics such as Anthony Lane of The New Yorker criticized the overall plot of the film, writing, "if there was anything to understand, it wasn't worth the sweat."
Avengers: Age of Ultron currently holds an audience score of 83% on Rotten Tomatoes.