If asked to name our favourite films, few of us have a problem rolling off a list of must-sees. After all, there are so many great flicks to choose from, aren't there? And if you're worried your choices might make you look a bit silly or unintelligent, there's loads of help at hand. Needless to say, certain movies crop up in those 'best ever' lists time and again: Casablanca, The Godfather, Trainspotting, Gigli…

Well, maybe that's going a bit far. However, we often delight in films without really knowing why we like them, and putting what grabbed us into words can be tough. After all, if all movies could be easily judged as simply good or bad, the Hollywood money-making machine would've reached its nirvana. No, what we want to know this week is a little trickier than your favourite movie. What we want to know is: what makes a great film great?

• Does it need to have a star name or two, or are lesser known actors equally capable of creating a real winner?

• Do the best films usually have the biggest budgets (not counting Waterworld, of course)?

• Are there certain devices, such as a plot twist, that all great movies must have?

• Are non-Hollywood films often better because they don't require, say, a happy ending?

• Does the director make the film, rather than the actors?

• Do all the best films have a great script, or can the likes of special effects more than compensate for cheesy one-liners?

• Are your favourite films mostly based on books, or is not knowing the story already essential to your viewing?

• Do the greatest films have mass appeal, or are you an art house enthusiast?

• Finally, are the best directors usually highly trained professionals, or often self-taught?