The 2010 summer moviegoing season is in full swing, with Shrek Forever After leading the box office surge last weekend (taking in a respectable, but not earth-shattering $71 million), and now we're approaching one of the biggest weekends of summer: Memorial Day weekend. The three-day holiday weekend has played host to several blockbusters over the years, and 2010 is no different with a couple big heavy hitters entering an already packed marketplace. Let's take a look at this week's competition …