RELATED: The 25 Biggest Movies of All Time at the Box Office

There were some huge surprises at the box office this Memorial Day weekend as two highly anticipated summer films, Sex and the City 2 and Prince of Persia: The Sands of Time, failed to take the top spot away from last week's reigning champ, Shrek Forever After.

The forth installment of DreamWorks Animation's phenomenally successful Shrek series, was predicted to drop to third place this weekend but instead out earned both high profile new films with an additional $43.3 million. The film, stars the returning voice talents of Mike Myers, Cameron Diaz, Antonio Banderas and Eddie Murphy. While the film may have dropped around 38% from the previous week, it was added in eight new theaters for a total of 4,367 earning around $9,926 on each screen. The film has now earned $133 million in just two weeks at the box office nearly earning back it's $165 million production cost.

Despite early reports that the film had earned nearly $3 million at midnight showings on Thursday and $14.2 million on Friday alone, that apparently wasn't enough for Sex and the City 2 to take the number one position at the box office this weekend. The film, which is a sequel to the extremely successful 2008 film, Sex and the City: The Movie, based on the popular HBO series was predicted to be number one this weekend earning $65.5 million but instead came up short only taking second place with about $32.1 million, nearly half of it's predicted earnings. The film features returning stars Sarah Jessica Parker, Kim Cattrall, Kristin Davis and Cynthia Nixon and opened on 3,445 screens earning $9,926 on each. The film is predicted to earn $46.3 million for the four day holiday weekend, including it's midnight screenings, which brings the film almost half way to earning back it's $100 million production cost.

Also failing to live up to early predictions was the new film from Disney Studios and super-producer Jerry Bruckheimer, Prince of Persia: The Sands of Time, which is an adaptation of the classic video game. The film, which stars Jake Gyllenhaal, Gemma Arterton (Clash of the Titans), Ben Kingsley and Alfred Molina, fell short of it's predicted $61.1 million second place earnings, coming in at third this weekend and only making half of it's predicted total. The film was seen on 3,646 screens and earned almost $8,275 on each for a weekend gross of around $30.1 million, which is not even close to earning back its $200 million purported budget cost.

Falling back two spaces from last week to number four is undeniably this summer's biggest hit so far, Iron Man 2. The film, which is directed by Jon Favreau, stars Robert Downey Jr., Gwyneth Paltrow, Don Cheadle, Mickey Rourke, Sam Rockwell, Scarlett Johansson and Samuel L. Jackson. The film dropped nearly 40% in it's forth week on the charts and was actually seen in three hundred and seventy-three less theaters than the week before. The film was predicted to take the forth spot this week but earned a bit less than its predicted $19.2 million, earning around $16 million. The movie made about $4,215 on each of its 3,804 screens, bringing its total domestic gross to an impressive $274 million. The film has now earned about $550 million worldwide in just under a month, placing it at sixty on the highest grossing films of all-time list.

Finally, rounding out the top five this week and doing better than predicted is Ridley Scott's Robin Hood. The film stars Oscar winner Russell Crowe as the famous bow & arrow wielding hero, along with fellow Oscar winners Cate Blanchett and William Hurt, and accomplished actors Mark Strong (Kick-Ass) and Danny Huston (X-Men Origins: Wolverine) rounding out the cast. The film dropped 45.1% from the previous week and was seen on one hundred and thirty-two less screens for a total of 3,373 earning $3,055 on each. The movie earned an additional $10.3 million this week, which was more than its predicted $8.8 million total. The film has now earned $83 million domestically in three weeks but has earned an impressive $154 million overseas for a worldwide total of $237 million, which surpasses it's initial $200 million production cost.

Doing well in its opening weekend in limited release is the French film, Micmacs, from director Jean-Pierre Jeunet. The film, which debuted on only four screens it earned $12,175 on each for a total of $48,700.

Continuing to do extremely well in limited release the Argentine film, The Secret in Their Eyes, by acclaimed director Juan José Campanella and starring Ricardo Darín. The film rose an impressive 4.8% in its seventh week on the charts, adding 14 theaters for a total of 155 and earning $3,019 on each for a weekend total of $468,000, bringing the films total gross to around $3.3 million.

Also, continuing to do well in limited release is Please Give, which stars Catherine Keener, Amanda Peet and Oliver Platt. The film, which only dropped 10.8% this week was also seen in three less theaters but still managed to earn an additional $211,000 in its fifth week. The film was seen on 50 screens and managed to earn $4,220 on each screen. The movie has now earned around $1.3 million in just five weeks on the charts.

Next weekend will see the summer box office heat up again with four highly anticipated new films in wide release. First, the sci-fi thriller Splice starring Oscar winner Adrien Brody (The Pianist) and actress/director Sarah Polley (Away From Her) as genetic engineers who make a fateful mistake while experimenting with splicing human and animal DNA together.

Also next week is the release of the new action comedy Killers starring Katherine Heigl (Grey's Anatomy) as an average woman unknowingly engaged to an international super-spy played by Ashton Kutcher (Valentine's Day).

Marmaduke, the beloved cartoon canine, comes to the big screen next week with a film that stars an all-star cast, which includes Owen Wilson (Marley & Me), William H. Macy (Fargo), Kiefer Sutherland (24) and Emma Stone (Zombieland).

Finally, next week will see the release of the long awaited rock n' roll comedy Get Him to the Greek, produced by Judd Apatow (Superbad) and written by Jason Segel (Forgetting Sarah Marshall). The film stars Jonah Hill (Superbad) as a record company assistant who is told by his boss (Sean Combs) that he has three days to get a washed-up, alcoholic rock singer played by Russell Brand (Forgetting Sarah Marshall) from London to Los Angeles for his comeback show. So please check back in seven days to see who comes out on top at the box office next week!