Having gone and seen Serenity twice over this weekend (and enjoying it immensely each time), I'm left thinking about what I would consider my favorite movie of all time.
Several possibilities for me, incuding Star Wars (A New Hope, the original Star Wars), Goodfellas (Pesci was so delightfully bad in that movie), Top Gun (cheesy, but enjoyable), and a batch of other films that I could list, including some old classics, some classic "war movies" with John Wayne, Clinton Eastwood, and others (including The Dirty Dozen, Kelley's Heroes, and others). I should also include the Indiana Jones movies (which were excellent), many of the Bond classics, and more.
I really enjoyed Serenity, and think it was very well done. But I don't know that I would say it's my all time favorite. Close I think, but when forced to choose I'm gonna go with Star Wars still. It launched SciFi as a truly effective genre for big screen movies. Yes, there were other big SciFi movies, including 2001 and a few others, but the amount of money that Star Wars took in set records for success. The marketing of figurines, light sabers, laser pistol toys and other similar items taught the world that having a tie-in to a success movie can do wonders for your industry.
Anyway, I'd like to see other peoples choices for what their own favorites are. There's no right or wrong answers, it's just your opinion, but it may help a bit if you explain why you feel your choice should rank as a favorite.