When director Guy Ritchie (“Lock, Stock and Two Smoking Barrels,” “Snatch”) and actor Robert Downey Jr. updated the Sherlock Holmes mythos in 2009, they delivered an appealing blend of action, drama, mystery and suspense. Sadly, their return to the well is less appealing. That’s not to say “Sherlock Holmes: A Game of Shadows” is a disaster. Downey Jr. is still outstanding in the title role, most notably because he gives the master detective a sense of brutishness that isn’t typically seen in the character.