Why is “Mann” it this sentence needs to be “Dem Mann” and not “Der Mann”?
Sentence: Dem Mann gefallt das Hotel nicht

gefallen is one of those verbs that takes a direct object in  the dative.

See the video for an explanation
https://www.youtube.com/watch?v=Yy7NPmWgaTk

I see.

Is there a list of verbs which does that?

The video gives you some of the most common dative verbs.

For more google: german dative verbs

Hallo RexV und sfpugh!

Thanks for sharing that resource sfpugh!

To clarify this a little more, RexV, sfpugh is correct: gefallen always takes the dative. This is because although it is commonly translated as "to like," gefallen doesn't really work like "to like" in English - it is closer to "to be pleasing."

In the English construction for this sentence, we would say "The man doesn't like the hotel," but a more literal translation of the German would be closer to "To the man the hotel is not pleasing." Because of that "to the man" meaning, we need to use the dative.

I hope that this clears things up a little more!

Tschüss!

Liss