'Shrek Forever After'In the biggest upset of the year so far, the ogres defeated the cougars. 'Sex and the City 2' went into Memorial Day weekend as the expected champion; instead, it may have to settle for third place as 'Shrek Forever After' remains the top ticket-seller in its second week.

Studio estimates for the four-day weekend have 'Shrek' finishing with $55.7 million, for a total of $145.5 million since it opened 11 days ago. That includes an estimated $12.4 million earned on Monday's holiday. The film's Friday-to-Sunday total is $43.3 million, down just 39 percent from last week's underwhelming opening.

Duking it out for second place are 'Sex' and fellow newcomer 'Prince of Persia: The Sands of Time.' Like 'Sex,' 'Prince' opened well below expectations, but early estimates suggest moviegoers preferred Jake Gyllenhaal's flexing pecs to 'Sex.' The four-day estimates give 'Prince' a scimitar-thin edge, with $37.8 million over $37.1 million for Sarah Jessica Parker and company. The three-day Friday-to-Sunday totals, however, had put 'Sex' ahead with $32.1 million to 'Prince's' $30.2 million. We may not have a definitive winner until final numbers are released on Tuesday. 'Shrek Forever After'In the biggest upset of the year so far, the ogres defeated the cougars. 'Sex and the City 2' went into Memorial Day weekend as the expected champion; instead, it may have to settle for third place as 'Shrek Forever After' remains the top ticket-seller in its second week.

Studio estimates for the four-day weekend have 'Shrek' finishing with $55.7 million, for a total of $145.5 million since it opened 11 days ago. That includes an estimated $12.4 million earned on Monday's holiday. The film's Friday-to-Sunday total is $43.3 million, down just 39 percent from last week's underwhelming opening.

Duking it out for second place are 'Sex' and fellow newcomer 'Prince of Persia: The Sands of Time.' Like 'Sex,' 'Prince' opened well below expectations, but early estimates suggest moviegoers preferred Jake Gyllenhaal's flexing pecs to 'Sex.' The four-day estimates give 'Prince' a scimitar-thin edge, with $37.8 million over $37.1 million for Sarah Jessica Parker and company. The three-day Friday-to-Sunday totals, however, had put 'Sex' ahead with $32.1 million to 'Prince's' $30.2 million. We may not have a definitive winner until final numbers are released on Tuesday.

Sarah Jessica Parker in 'Sex and the City 2'Still, both Warner Bros. ('Sex') and Disney ('Prince') have to be disappointed. Predictions for 'Sex's' four-day take ran as high as $75 million, taking into account the $56.8 million opening of the first movie two years ago, the lack of other women-targeted movies playing, and the anticipation and hype built up for the sequel. Even adding the $14.2 million 'Sex' snagged in early screenings on Thursday, that's still only $51.4 million for five days, less than what the first 'Sex' earned in three days.

It's possible that the film was hurt by poor reviews, its R-rating, and its 2 1/2-hour running time (allowing for fewer screenings per day) or its inability to attract male moviegoers (polling found the 'Sex 2' audience to be 90 percent female), but none of these proved obstacles for the first movie. Maybe it's just that real-life women the ages of Carrie or Samantha were busy taking their kids to see 'Shrek.'

As for 'Prince,' it had seen predictions as high as $54 million for the four-day opening. It may have been hurt by weak reviews, a PG-13 rating that discouraged younger kids, or (most likely) the continued presence in theaters of 'Shrek' as the preferred fairy-tale adventure.

'Iron Man 2' was fourth. It earned $16.3 million from Friday to Sunday (down 39 percent from last week) and a total of $20.6 million over the four-day weekend. In fifth place was 'Robin Hood,' with $10.3 million (down 45 percent) from Friday to Sunday and $13.5 million for the whole holiday weekend.

The full top 10 (four-day totals):

1. 'Shrek Forever After,' $55.7 million (4.367 screens), $145.5 million total
2. 'Prince of Persia: The Sands of Time,' $37.8 million (3,646), new release
3. 'Sex and the City 2,' $37.1 million (3,445), $51.4 million
4. 'Iron Man 2,' $20.6 million (3,804), $279.2 million
5. 'Robin Hood,' $13,5 million (3,373), $86.3 million
6. 'Letters to Juliet,' $6.2 million (2,825), $38.0 million
7. 'Just Wright,' $2.7 million (1,195), $18.7 million
8. 'Date Night,' $2.3 million (1,126),$93.9 million
9. 'MacGruber,' $1.9 million (2,546), $7.6 million
10. 'How to Train Your Dragon,' $1.5 million (825), $213.1 million

Top 10 summer 2010 movies:

1. 'Iron Man 2,' $279.2 million total
2. 'Shrek Forever After,' $145.5 million
3. 'Robin Hood,' $86.3 million
4. 'Sex and the City 2,' $51.4 million
5. 'Letters to Juliet,' $38.0 million
6. 'Prince of Persia: The Sands of Time,' $37.8 million
7. 'Just Wright,' $18.7 million
8. 'MacGruber,' $7.6 million
9. 'Babies,' $6.1 million
10. 'Kites,' $1.6 million

• Follow Gary Susman on Twitter @garysusman.