There are minor spoilers ahead, especially for those familiar with Arthur Conan Doyle's Holmes stories.
Guy Ritchie's Sherlock Holmes butted right up against the boundaries of revisionism, using little-known aspects of the Holmes canon (his baritsu skills, for instance) to create a rollicking adventure starring the world's greatest detective. There was a hint of freshness to the film, and the chemistry between Robert Downey Jr's Holmes and Jude Law's Watson bouyed up a CG-heavy bunch of silliness.
Now the gang is back together, but the touches that made the first film a surprise seem to have disappeared. The Holmes/Watson relationship is now shrill (probably because Hollywood Blockbuster Screenwriting for Hacks 101 says they have to have a 'journey'), the facade of a mystery story has been chucked for a nation-hopping action adventure, and the volume has been turned up to 12, starting with a gibbering, strung out Holmes and never quite simmering down.
Oh, and it plays with the deep Holmes mythology - when, in the first act Mycroft Holmes (Sherlock's brother, a spy, and a real character from the stories) says he's going to a peace conference in Reichenbach, Switzerland, even casual Holmes fans will know what that bodes.
Game of Shadows opens after most of the canon Holmes stories have taken place, with Watson moved out and about to be married. Holmes has descended into a cocaine mania focusing on Moriarty, with whom he has already crossed wits on many cases. But this film has little patience for building a mystery about Moriarty's deeds - right from the opening narration we know that the Napoleon of Crime has been behind a series of bombings intended to send Europe into World War I a decade early. And so from the start there's no throughline of discovery, simply a slack chase of Moriarty as he goes on a European book tour/attempts to bring about the end of Western Civilization (seriously. He's multitasking).
To get some element of mystery, the movie has Holmes run into a gypsy whose brother is implicated in some aspect of Moriarty's scheme. She is a blank, pointless character who tags around for the remainder of the movie for no good reason; original Lisbeth Salander Noomi Rapace plays the gypsy woman with a dense blankness, refusing to give the character any spark of life. She doesn't even come into play as a potential love interest, nor does she have any real particular talents that make her integral to the story. They just needed a girl for the trailer, I guess.
Jared Harris, aka Lane Pryce from Mad Men, is Moriarty. What seemed like an inspired bit of casting ends up failing in the face of an unstoppable force: Robert Downey Jr's need to consume every inch of the frame like an angry sun going supernova. Harris' Moriarty is a buttoned down, seemingly normal guy hiding an interior of sheer madness - ie, the exact opposite of Downey's outwardly wacky, inwardly totally rational Holmes - and I imagine that contrast worked on paper. In the film it means that Harris is crushed under Downey's manic energy and charisma.
It turns out that the film has an actor who would have made a great Moriarty opposite Downey - Stephen Fry, who plays Mycroft (and who has an extensive nude scene that honestly pushes the boundaries of the PG-13). Fry has an expansive personality and presence that refuses to be bowed in his scenes with Downey, and while they aren't a great physical match - Fry towers over the hero - that energy is what the villain needed. Instead Moriarty sort of fades into the woodwork.
What's worse is that the script shortchanges Moriarty big time. There's one great scene where we see how Moriarty has outwitted Holmes, but there's no feeling of mental cat and mouse, which should be the whole crux of the film. The final confrontation between the two contains a bunch of random chess dialogue ("Rook to King's pawn. Mate!"), but that feels more like a dumb person's idea of how these two smart guys would interact than anything real. It's disappointing when Moriarty's method for getting information out of Holmes is sticking a huge meathook in his shoulder and torturing him. Really, that's the best he could come up with? Something that blunt and ham handed? Most Bond villains - which is what Moriarty has been turned into - would scoff at that.
The action quotient feels amped up this time, and Guy Ritchie just lets loose stylistically, never worrying about what any of his stylistic tics should MEAN. There's a scene where our heroes escape from the bad guys in the woods, pursued by gunmen and giant cannons, that's played out in a hyper bullet-time/Zack Snyder in the K-hole style. It looks cool, but it doesn't mean anything, coming across just as an effect that Ritchie liked. The sequence feels like a perfume commercial - Exploseeve, a new fragrance by Guy Ritchie. It looks cool but has no visceral feeling or impact.
This time out Downey and Law are reduced to just being a bickering couple, the Lockhorns of the Victorian mystery world. It's tiring, and it's not fun. The film has some strong set pieces, but it has nothing between them. This is where the Holmes/Watson stuff saved the day in the first film, smoothing over the plot mechanics that got the characters from set piece to set piece. This film is trying really hard to be an Indiana Jones movie, so they just slide from set piece to set piece, leaving little for Holmes and Watson to do together but have Jude Law play varying shades of exasperated. This is probably the biggest disappointment of the movie; I could maybe make an argument that turning Holmes into a 30s pulp spy is acknowledging the descendents of Arthur Conan Doyle's original serialized stories, but why make that argument if the movie you're arguing about isn't that much fun?
The script, by Michele Mulroney and Kieran Mulroney, is predicated on one weird concept - one that is a spoiler, but if you instantly understood what Reichenbach means for Holmes, you already know what the concept is. To be unspoilery for the layman, this film is set very near the end of the Holmes/Moriarty conflict; when the film opens the two geniuses have been sparring for some time. In cinematic terms it's weird because it feels like a second movie is missing, like this is the end of the Moriarty trilogy. We missed the point when the shadowy figure in the first film became a full-fledged character, and instead we're left with the end game of the rivalry. I don't know if better writing for Moriarty would have helped, of if casting someone with more verve than Harris would have been the answer, but this movie tells of a seminal moment in Holmes lore, yet it never feels as epic as it needs to be.
Game of Shadows is a tired sequel, a movie that doesn't quite understand what worked in the first film. It seemed like Robert Downey Jr had a chance to forge an interesting chapter in the history of Holmes adaptations, but now it looks like he's going to be an asterix while the BBC modern take, starring Benedict Cumberbatch, will probably be the defining Holmes of our time.