As for the filthy apartment ... in the written stories, Holmes was pretty much a slob. London was never described overall as being awful and filthy, but I read a bio of Conan Dolyle, who was origially from Edinburgh, Scotland. Doyle was very happy to leave that city because it was absolutely horrid, filthy, and grim.
Regarding Holmes’s apartment, yes, Doyle described it as untidy, but in the Downey film it looked disgustingly DIRTY. And where Rathbone’s Holmes was well-dressed, and Brett’s Holmes was downright dapper, almost a fop, Downey’s was rather sloppy. But I actually liked the Downey film better than I thought I would because they didn’t contemporize Holmes as much as I thought they would, apart from the aforementioned sartorial issues. I thought they’d have Holmes jumping in and out of bed with women and possibly men, and Freudianizing the whole thing. Yes, they introduced a mild sexual element, but it was at least consistent with Holmes’s expressed admiration for Irene Adler in the original stories.
Sherlock Holmes and Dr. Watson go on a camping trip. After a good dinner and a bottle of wine, they retire for the night, and go to sleep.
Some hours later, Holmes wakes up and nudges his faithful friend. “Watson, look up at the sky and tell me what you see.”
“I see millions and millions of stars, Holmes,” replies Watson.
“And what do you deduce from that?”
Watson ponders for a minute.
“Well, astronomically, it tells me that there are millions of galaxies and potentially billions of planets. Astrologically, I observe that Saturn is in Leo. Horologically, I deduce that the time is approximately a quarter past three. Meteorologically, I suspect that we will have a beautiful day tomorrow. Theologically, I can see that God is all powerful, and that we are a small and insignificant part of the universe. What does it tell you, Holmes?”
Holmes is silent for a moment. “Watson, you idiot!” he says. “Someone has stolen our tent!”