"That's My Boy" might be the funniest Adam Sandler comedy in a decade, but audiences wouldn't know: the R-rated laugher earned just $4.6 million on Friday night, putting on track to earn just $13 million through the weekend. That would give Sandler his worst opening weekend since "Reign Over Me" in 2007, and his worst for a live-action Happy Madison-production since "Little Nicky" in 2000. Things weren't much better for Tom Cruise.