It didn't take long, after the success of the original, for the makers to head straight for the Big Bad in the Sherlock Holmes universe. The second movie sees Holmes (Downey), Watson (Law) and a conveniently-passing gypsy fortune-teller (Rapace), take on Professor Moriarty (Harris), as he plots to acquire a slew of businesses which would profit from a war, then trigger the war with an escalating series of assassination of key political figures. That involves roaming around between London, France and Germany, with a final encounter high in the Swiss Alps, where a mountain-top fortress is host to a peace conference. If you've read the relevant Conor Doyle works, you will not be surprised to hear that this also has an F-sized waterfall located right beneath a balcony. However, I don't recall there being quite as many things blowing up, gun battles, or Parkour-trained Cossack assassins in the Victorian books.
And that's perhaps the issue. Sherlock Holmes in the books, may have had some pugilistic skills, but he never needed to use them, because his mind was so superior that violence was never needed to resolve problems. Here, it seems almost the first resort, not the last, and there's only a couple of sequences where Holmes' mad detective skillz prove significant. That's a shame, because the result is, while slickly produced and never dull, there's precious little here to separate this from any modern action flick, except for the bowler hats and other period elements. I don't mind updating Holmes for a modern era, but there's not much point if you're going to throw out everything that made the character unique - the Steven Moffatt version on the BBC, did a much better job of creating a 21st-century Holmes.
Still, that said: if you think of this less as anything to do with the great detective, and more as a steam-punk version of a Bourne or Bond movie, then it's by no means disastrous. Harris is actually pretty good as the arch-nemesis, and makes a far better impression than... whoever it was in the first one [which says a lot], while the set pieces are generally well-constructed and nicely put-together - particularly memorable is a sequence where our heroes are legging it away from an arms factory they've just demolished, under a rain of fire from German soldiers, that escalates up to a round from "Little Hansel". The film is certainly not short on action, adventure or excitement. It is, however, largely devoid of heart and emotional resonance.