What I enjoyed was that most of the entire film was about family. In the end, what mattered most was loved ones. They were what was most important to nearly all of the characters.
Tony Stark finally realizing that he had to sacrifice himself to save all the loved ones for the others ahead of his own family's needs has one of the most amazing things that I have ever seen on film.
To see Steve Rogers finally able to be with his one true love, Peggy Carter, warmed the heart.
And the list goes on: Clint reunited with his. Natasha referring to the Avengers as her family and then making the ultimate sacrifice for her friend and teammate. Bruce trying to bring Natasha back, knowing that she had loved him. Scott risking everything to see his daughter. Thor's reunion with his mother and Tony's encounter with his father. Peter's excitement at seeing his father figure, Stark, still alive. The sadness Clint and Wanda felt knowing that loved ones would never return. Other Avengers are also reunited with family. It is tremendous and it drives the film.
Rocket acknowledges that the Guardians are family. We even see the family dynamic between Nebula, Gamorra, and Thanos (as dysfunctional as it is!).
The theme of family and love permeates the film. It also involves friendships: Bucky and Sam with Cap, Happy and Tony, Clint and Natasha. But even those are based on the characters love and caring about one another.
With all of that love, family, and friendship, how could I not like this film. In the end, that is what won the day. Kudos to the directors, Anthony and Joe Russo for a film that can be enjoyed by all (especially, we long time fans of Marvel Comics and characters). As Stan the Man would have put it, "Excelsior!"
