Perhaps this isn't really a reason why Elementary is better than Sherlock, but a statement about how when Elementary came along they at least had some realisation that it was going to be watched by fans of Sherlock. In writing the characters like they have with those plots, they've allowed room for both series in our hearts. When watching Sherlock's third season, I don't feel like I'm having a fling before going back to Elementary afterwards. You can't say that any of the characters are the same in either series, they are all different and not just because they've been played by different characters. Not only the main characters, but the supporting cast too. But Elementary show them in a better light one of the key points in the first episode of season three of Sherlock was that the surprise element of Sherlock's fall (at least in one dubious version) was that Molly Hooper was in on it. But this wouldn't work in Elementary, because there isn't a naïve character who could be a surprise element. For example it would be no surprise to find Marcus Bell in the middle of a complex plot and right now that character is undergoing an interesting and unexpected angle. Which shows that even minor characters in Elementary are free to evolve, whereas in Sherlock it seems that character change is unexpected and to be used as a surprise.