Woody Allen has always viewed human relationships as ephemeral, short lived, changeable. His early great films Annie Hall (1977) and Manhattan (1979) are studies in shifting relationships, couples who pair up for a time and then go their separate ways, looking for other partners. The nostalgia of love lost drove these early films. Allen's view of such relationships darkened significantly in the 1980s and 1990s with such films as Hannah and Her Sisters (1986), Crimes and Misdemeanors (1989), and Husbands and Wives (1992).
So we come to the question of why we should find interest in Vicky Cristina Barcelona (2008). It is not a comedy. It is not really a romantic film either. Maybe the best way to describe it is as a character study.
The characters in Vicky Cristina Barcelona hold differing opinions about relationships, and they enact those views. Vicky (Rebecca Hall) is a middle-of-the-road art history graduate student who believes that love is forever and has chosen as her future husband a bland, corporate drone. Cristina (Scarlett Johanssen—one of Allen's favorite actresses) has a more conflicted attitude. Although she says she doesn't believe in monogamy, she does believe in the possibility of finding the perfect partner, but she also chafes at the confinement of long-term relationships. For Maria Elena (Penelope Cruz) relationships mean struggle—her long-term affair with the artist Juan Antonio Gonzalo (Javier Bardem) is a constant battle against and with a person she needs so much that she resents and resists him. Juan Antonio doesn't necessarily have a position on relationships. He goes with the flow. His easy attitude pays off for him. When Cristina tells him that she is not satisfied with their relationship and that she needs time to herself, he accepts her decision, while Maria Elena wants to attack her. One can view Juan Antonio's reaction as post-feminist male enlightenment, or as cynicism—I tend towards the latter view.
I suppose the interest of the film for Allen lies in the constantly shifting array of human connections. Cristina believes that in Juan Antonio she at last has found the perfect partner, but then she grows dissatisfied. Vicky resents and dislikes Juan Antonio but after sleeping with him discovers that she loves him—until Maria Elena tries to shoot her, whereupon she returns to her bland fiancé, who by the end of the film she has married. Even Vicky's aunt, who provides the house where Vicky and Cristina live while in Spain, is dissatisfied with her marriage. Nothing is fixed.
The setting—Barcelona—is beautiful, though it has no particular bearing on the plot. Maybe for the two young American women who go to Spain for a brief respite from their studies, it is an exotic place of adventure and romantic intrigue—they can dally there, experience freedom briefly—then leave. Are they changed? Does anything of importance really happen in this film? Are human destinies determined? The film ends in the middle of things. Nothing is resolved. No single character's point of view prevails. Rather, the film shows that people believe what they believe and that they tend to act on their beliefs, for better or worse. Life goes on.
There's a sort of clinical indifference in how this film treats Vicky and Christina and Maria Elena. Allen seems interested in what will happen to them, which choices they will make, how they will fare in their various entanglements—but there's no erotic or emotional or passionate engagement with his subject. Maybe for Allen, now in his 70s, romance is more a matter of clinical interest than of anything else.