Fiona and Shrek in 'Shrek Forever After'In another slow week at the summer box office, it was once again the ogre who was the biggest source of green. 'Shrek Forever After' fought off challenges from a rock star, an assassin, a Great Dane and a mutant to top the chart for the third straight week.

As expected, 'Shrek' dipped about 40 percent from last week to finish with an estimated $25.3 million. It's still underperforming compared to the first three 'Shrek' movies, but this weekend's haul brought it that much closer to the $200 million mark, a threshold that only 'Iron Man 2,' among all this summer's movies so far, has crossed.

Among new releases, 'Get Him to the Greek' fared best. The comedy debuted at No. 2 with $17.4 million. Its per-screen average of $6,460 was the best of all current wide-release movies. Action/romance 'Killers' was close behind, opening at $16.1 million for a third-place finish. Fiona and Shrek in 'Shrek Forever After'In another slow week at the summer box office, it was once again the ogre who was the biggest source of green. 'Shrek Forever After' fought off challenges from a rock star, an assassin, a Great Dane, and a mutant to top the chart for the third straight week.

As expected, 'Shrek' dipped about 40 percent from last week to finish with an estimated $25.3 million. It's still underperforming compared to the first three 'Shrek' movies, but this weekend's haul brought it that much closer to the $200 million mark, a threshold that only 'Iron Man 2,' among all this summer's movies so far, has crossed.

Among new releases, 'Get Him to the Greek' fared best. The comedy debuted at No. 2 with $17.4 million. Its per-screen average of $6,460 was the best of all current wide-release movies. Action/romance 'Killers' was close behind, opening at $16.1 million for a third-place finish.

The week's other new wide releases didn't even crack the top five. With family audiences still favoring 'Shrek,' 'Marmaduke' opened below expectations with $11.3 million, finishing sixth. Sci-fi/horror film 'Splice,' chasing many of the same viewers who went to see 'Greek' and 'Killers,' opened with $7.5 million to land at No. 8. (It was edged out by 'Iron Man 2,' which earned just $333,000 more, enough to finish in seventh place.)

Rounding out the top five were holdovers 'Prince of Persia: The Sands of Time' (No. 4, $13.9 million) and 'Sex and the City 2' (No. 5, $12.7 million). As expected, both fell more than 50 percent from their debuts last week.

The search for an all-bases-covered summer blockbuster continues. This week's four new releases earned a combined $52.3 million, far below the $68.1 million that Pixar's 'Up' earned when it debuted this same weekend last year. We'll probably have to wait for the next Pixar movie, June 18's 'Toy Story 3,' for a movie with similarly broad appeal.

The full top 10:

1. 'Shrek Forever After,' $25.3 million (4.386 screens), $183.0 million total
2. 'Get Him to the Greek,' $17.4 million (2,697), new release
3. 'Killers,' $16.1 million (2,859), new release
4. 'Prince of Persia: The Sands of Time,' $13.9 million (3,646), $59.5 million
5. 'Sex and the City 2,' $12.7 million (3,445), $73.4 million
6. 'Marmaduke,' $11.3 million (3,213), new release
7. 'Iron Man 2,' $7.8 million (3,007), $291.3 million
8. 'Splice,' $7.5 million (2,450), new release
9. 'Robin Hood,' $5.1 million (2,599), $94.3 million
10. 'Letters to Juliet,' $3.0 million (1,962), $43.3 million

Top 10 summer 2010 movies:

1. 'Iron Man 2,' $279.2 million total
2. 'Shrek Forever After,' $183.0 million
3. 'Robin Hood,' $94.3 million
4. 'Sex and the City 2,' $73.4 million
5. 'Prince of Persia: The Sands of Time,' $59.5 million
6. 'Letters to Juliet,' $43.3 million
7. 'Just Wright,' $20.2 million
8. 'Get Him to the Greek,' $17.4 million
9. 'Killers,' $16.1 million
10. 'Marmaduke,' $11.3 million

• Follow Gary Susman on Twitter @garysusman.