This topic is subjective and can vary from one person to another. But for me, the anime series of Yu Yu Hakusho or also known as Ghost Fighter is better than the manga. Yusuke, the main character of the story, were enemies with Kuwabara. But when Yusuke died in a car accident, Kuwabara was very emotional with his death and when Yusuke was brought to life, they became friends and formed a spiritual team.
You can be emotional when watching the anime series because of the music that is very proper to each scene and the voice actors are really bring life what you are imagining in the manga series. Generally, the plot and story are very good whichever you like better.
This is another widely debated topic. There are many manga enthusiasts that would say all mangas are superior to their animated counterparts but there are a few anime which most people can agree turned out better than the manga. Most of these have more to do with being very action oriented with a lot of fight scenes which will almost always be executed better on screen than in text.
Some of these include Overlord, Gintama, and a racing anime/manga called Initial D. Many people also consider Sailor Moon's anime adaptation to be mmuch better than the manga.