I could watch Scott Pilgrim whenever, and I probably wouldn't get bored of it. Second only to Get Him to the Greek in terms of films I put on when I'm cleaning, and have seen several dozen times. The movie is extremely clever, but as already stated it had an incredible niche appeal. If you're not a gamer, or if you really weren't influenced heavily by Gen Y culture, the movie is probably going to seem really stupid to you.
Then again, Alien is a terrifying, yet wholly thrilling piece of cinema. It still stands after all these years as one of the best sci-fi films ever, and I probably take it in once a year, if not more. Iconic, would be a good (yet over-used) word.
I guess you could say Alien is a better film to a wider audience of people. If there is such a thing as objective superiority, it has it. But do I want to vote for the movie I love once a year, or the movie that keeps me coming back once every month or two? I don't know. Convince me.