Love is a very popular theme because it conjures such strong emotions. Stories concerned with love can produce very touching stories such as "Love Actually" or very dramatic stories such as "Romeo And Juliet" -- which is about forbidden love, but in the end love conquers all, and the protagonists would rather die than be apart.
Friendship is also a strong theme and can make for very touching stories -- the endurance of friendship over all obstacles and distances, such as in "The Shawshank Redemption," will always warm the heart.
Overcoming obstacles is always a good theme because it builds the protagonists' character -- it makes them whole and brings them to the end of their journey. The obstacles will depend on the plot -- it could be as straightforward as a quest such as in "The Lord of the Rings," or it could be less literal, such as a drug addict overcoming his addiction such as in "Trainspotting."
A protagonist who must go on a journey to realize her potential, and in some cases accept her destiny, is always a winning theme because again it builds her character and makes for a fulfilling story. For example, in "The Matrix" we are told Neo is destined for greatness -- at first he does not believe in himself, but as the story progresses, both the audience and the character have the pleasure of seeing him fulfill this greatness.
Revenge is always a very interesting theme. It means, by definition, that the story is going to be thrilling -- someone has been wronged, and we will see how justice is exacted. 'Hamlet' is a great example of this; the whole story is about his thirst for revenge due to the cold-blooded murder of his father. And of course, the act of revenge can have all kinds of interesting consequences.
Racial issues as themes can make for powerful stories because they can portray some awful, very real examples of intolerance. They can portray issues of human rights and can often be very close to the bone. For example, both "Schindler's List" and "The Diary of Anne Frank" portray the awful treatment of Jews at the hands of the Nazis during World War Two.
Redemption is always an interesting theme because it implies the protagonist has fallen, which immediately adds depth. It will follow that the protagonist will go on a journey to redeem himself -- this theme is therefore very strongly linked with the teaching of morals. In an article for Brighthub.com, Trent Lorcher states that in "Great Expectations," "Pip eventually realizes his great expectations, but not in the way he envisions. He sees the error of his ways and understands that happiness comes through doing good to others, as displayed by his treatment of Provis and Herbert, not through social status or wealth. His reconciliation with Joe demonstrates his willingness to embrace goodness, regardless of status."