Ohhh, I am so disappointed that no one here actual mentioned the german Naruto Opening. it is a "masterpiece" and deserves to be mentioned:
Though, on a serious note, I actually think the german One Piece opening was pretty great(though, I admit, you should be german to appreciate it):
Or the german Sailor Moon opening-
TIn the 90s everything had to be Techno in germany:
But back to the topic-
The JoJo OPs are mostly my favourites. Yeah, Bleach & Naruto had several great OPs, without any doubt(One Piece, of course, too), but I kinda love the JoJo OPs with their little details & the fact that they change over time.
Regarding the topic with Adaptions-
It's difficult. The Dom, an Internet-critic for Book->Movie adaptions(his videos are fittingly called "Lost in Adaptation") said several times, that a good adaption doesnt mean it overall a good product(which was already said in this thread, I know). Sometimes something which worked in the original media, doesnt have to work in its adaptation(That's also a reason why there are so many bad video-game movies. Because video games are supposed to be PLAYED, not watched!). For example, in books many thoughts & character-development happen in the head of the protagonist, something which doesnt really work in a movie. In Manga and Anime it's a little bit trickier, because they are quite similiar already. Ironically, I know an instant of a change, it happened in the first season of Attack on Titan. When Annie Leonhart got "unmasked", without spoiling too much, her reaction was a creepy smile in the manga. In the anime it was changed into a hysteric laughing fit, where she blushed. isayama himself ordered this change, so far I know, because he wanted her to portray more "human"- His opinion was, her reaction in the manga was too one-dimensional. Which I get. Still bothered me, because it was out-of-character and just... weird.
In the end, I wouldnt demonize changes, if necessary because it's another media, or if it's actual improvement to the source material. But there we also have to accept, that there will be endless discussions, when something is an improvement and what not.