By Nicole Sperling
Updated May 20, 2010 at 08:44 PM EDT

Image Credit: DreamworksIt’s summertime (at least at the box office) and Shrek Forever After kicks off the season’s animated kid flicks. With the Shrek series having grossed over $1 billion domestically, the fourth, and likely final, installment in the popular series is destined to be one of the top-grossing films this summer season. How high it opens is another question. It will be buoyed by the 3-D component, but a little bloom may have worn off this rose considering it’s been three years since we’ve had the green ogre in our theaters. Not to mention that the last two weren’t nearly as beloved critically as the original.

R-rated comedy MacGruber has the inauspicious task of going up against Shrek. The film — financed by Relativity Media, produced by Rogue, and released by Universal Pictures (that’s a mouthful) — is unlikely to light any fires at the box office despite the popularity of the Saturday Night Live character on the sketch comedy show. Read on for my predictions.

1. Shrek Forever After: $105 million

The first Shrek bowed to $42 million in 2001, while Shrek 2 opened to $108 million in 2004 and Shrek 3 grossed $121 million in 2007. Even with spotty reviews, inflation alone will propel this fourth iteration into $100 million plus territory. How high it gets is really a matter of how hungry audiences are for the top-notch voice cast of Mike Myers, Eddie Murphy, Cameron Diaz, and Antonio Banderas that have made the series so successful.

2. Iron Man 2: $26 million

The PG-13 rated actioner has already grossed $218 million stateside. Not bad for a film that’s not nearly as good as the original. After dropping 60 percent last weekend, the movie is likely to fall another 50 percent this frame. Whether it will hit the original’s domestic take of $318 million all depends on how it handles the stiff competition about to come its way.

3. Robin Hood: $18 million

With its revised gross from last weekend standing at $36 million and a B- from exit pollster Cinemascore, it is likely Robin Hood is headed for at least a 50 percent fall. It’s still earning impressive dollars overseas, but Universal will be lucky if they can collect more than $125 million from audience members on this side of the pond.

4. MacGruber: $8 million

This spy spoof looks a lot more like A Night at the Roxbury than Wayne’s World. Saturday Night Live has always been hit or miss when its wacky characters transfer to the big screen. It’s unlikely that Will Forte’s take on the MacGyver franchise has enough to sustain itself through an entire film. The studio hasn’t screened the film in advance for critics (never a good sign), so Relativity Media and producer Lorne Michaels should be happy campers if they can eke pass the $10 million mark.

5. Letters to Juliet: $7 million

The film’s a crowd-pleaser, so while it only grossed $13.8 million opening weekend, if word-of-mouth spreads, there’s a chance it can hold in for a better than 50 percent drop its second weekend in theaters. And it better do so fast. This is its only chance to shine before Sex and the City 2 drowns out this sweet romance.

Check back this weekend for updates on the box office.