Sherlock Holmes is always Sherlock Holmes. He’s a longstanding icon of fiction, and most interpretation of the character (such as the novels of Nicholas Meyer) stay reasonably true to the core of the character.
Batman, on the other hand, gets no respect. He’s generally written consistently for an abritrary period of time in a medium, and then poof! He’s somebody else. Some elements remain the same, but others… vanish.
There’s the Golden Age Comic Batman. Fighting Gangsters and weird criminals, occasionally killing, and quite the bon vivant - grinning in almost every panel one sees him.
In the 50’s, he mutated. No more killing, and lots of wacky scifi and time travel adventures.
In the 70’s he mutated again, probably as a backlash from the campy television series, into an actual detective. He became somewhat brooding. He was now an angry, angry man.
Post-Crisis, he’s darkened further, and become a borderline paranoid schizophrenic.
Of course, there’s the TV-Batman - completely goofy; there’s Movie-Batman-1 (AKA Edward Bataranghands), Gotham’s Gothiest; there’s Movie-Batman-2 (AKA Joel Schumacher’s leather fetish-boy) who’s just a lighter version of Movie-Batman-1.
There’s Animated-Batman-1, perhaps most like the 70’s Comic Batman, and Animated Batman 2, who’s similar, but a good bit lighter.
Now there’s Movie-Batman 3, also quite resembling the 70’s Batman.
Argh.
I feel the Batman portrayal we got from the 70’s and 80’s was the truest. He was the World’s Greatest Detective. He could legitimately rub shoulders with Superman, and take him down with Kryptonite boxing gloves should the need arise. He was capable of trusting people, though - and he was dark and brooding, but had lighter moments as well. He didn’t kill, and he didn’t like guns. Two other subsequent Batman interpretations have stuck most closely to this incarnation, as well.
I bring this up because a friend and I watched Batman Begins last night, and he (seeing it for the first time) commented that this version of Batman must not be a master scientist like the comic version, as Lucius was doing all the organic chemistry work.