One of the most important reasons why I love these movies is because of Gru. He is characterized to be a villain, but is likable enough in his emotions that the audience can empathize with him and cheer for him in the movies. Most villains are static characters, but Gru is very dynamic in emotion and motive, and that's what makes his internal conflict in the first movie so entertaining. He has a spectrum of emotions, and isn't necessarily all that evil despite being bad.