The Avengers would likely have a range of reactions. Captain America would respect the Incredibles' sense of justice. And the Hulk might just be confused at first but then find it cool.
If the Avengers watched The Incredibles, it could be a very interesting scenario. The Hulk might get a bit jealous seeing Mr. Incredible's strength at first. Black Widow would notice how Mrs. Incredible manages to be a great mother and a superhero at the same time. Hawkeye would be interested in the archery skills of any character in the movie who might use a bow. And they all could learn something about teamwork from the family's dynamic in the movie.
It depends on personal preference. Some people might like Marvel superheroes more for their diverse powers and relatable characters. Others might prefer DC superheroes for their classic and iconic status.
No. Since it's a 'lemon' fanfic, it likely contains inappropriate content. 'The Incredibles' is a family - friendly franchise, and a 'lemon' fanfic would go against the intended audience and values of the original work.
The original story of The Incredibles centers around a family of superheroes who try to balance their normal lives with their superpowers and face various challenges along the way.