My most favourite film in the entire Skywalker saga because of three things; love, patience and freedom.
Love - Han Solo and Princess Leia grow closely together in romance.
Patience - Luke Skywalker is very calm and confident in this film; e.g. green (which is the colour of his lightsaber) is my favourite colour.
Freedom - Destroying the Emperor, restoring freedom and justice to the galaxy, and Anakin Skywalker/Darth Vader (or Luke's father) joining back to the light side with ghosts of Yoda and Obi-Wan Kenobi is very heartwarming.
To be put simply, I love being on the light side and I love happiness, gladness and freedom.