It's a mix. 'Gangs of New York' is based on true events to a large extent. The movie depicts the gang warfare and the social situation in New York in the 19th century. However, some elements like the specific relationships between characters might be fictionalized for the sake of storytelling. For example, the general backdrop of different ethnic gangs vying for power was real, but individual story arcs were sometimes adjusted for drama.
The Gangs of New York is mainly a work of fiction. Although it's inspired by some elements of the historical period it portrays, the specific events and characters are largely created for the movie.
Definitely not. 'Gangs of New York' is a work of fiction that incorporates some aspects of the historical context but is not a true account of specific real-life events or people.
There are many facts in 'Gangs of New York'. The gangs in New York at that time were real, and the conflicts between different ethnic groups were also real. But fiction comes in when we look at the specific storylines of some characters. Maybe the individual heroic deeds or the way some relationships develop in the movie are more for entertainment value and not strictly historical.
The film 'Gangs of New York' has roots in true history. However, for cinematic purposes, some aspects may have been exaggerated or fictionalized to enhance the drama and entertainment value.