If you can't, declare them gracefully. Also mention (or don't review) films for which you have conflicts that might affect a reader's trust in you.

To put it slightly differently: This is NOT about your ability to be "objective"; it's preserving your readers' fragile trust, which can be undermined by your failure to disclose a potentially judgment-influencing connection. SPECIAL NOTE TO U.K. READERS: THIS KIND OF DISCLOSURE IS MUCH MORE IMPORTANT IN THE U.S. THAN IN BRITAIN, WHERE EDITORS MAY TOLERATE CONFLICTS AMERICAN EDITORS WOULDN'T.

A basic rule for book reviewing might be a good place to start for films, too: Never review a book by a friend or an enemy. The unfortunate corollary: You don't always know who your enemies are until you review their books.