I think one of the more interesting discussions can be about movies that you can feel confident recommending to just about anyone. This would be a movie that most people haven't seen. It might be a quiet masterpiece that flew under the radar. Basically, a movie that you think is so good and accessible that you can confidently recommend it to anybody and not worry that he or she will watch it, and come back to you the next day, and ask you why you made him or her waste two hours of his or her life.
For me, that movie is easily Dark City.
Realistically, the only person I'm aware of who arguably loved that movie more than me was Roger Ebert -- he actually did a commentary for the director's cut free of charge. I don't think that anybody I've recommended the movie to has responded as strongly as I did. That said, I've recommended it to a couple dozen people at this point and reactions have ranged from "Loved it! I can't believe I hadn't seen it!" to "Not my cup of tea; but, it was well made and I'm glad I saw it."
From my perspective, this is the perfect movie to generally recommend to people for a few reasons.
The low-hanging fruit is that The Matrix became a cultural phenomenon because people loved it. Dark City has similar themes to The Matrix. Dark City predates The Matrix (some of the sets built for Dark City were used in the production of The Matrix). And, Dark City is a better movie.
Dark City is also a movie that everybody should watch, particularly in this era of cinema, because we haven't seen many (possibly any) movies like it in nearly twenty years. It's an original screenplay that even Ebert said he thought was based on a comic book and was surprised to learn it was completely original. It's a film that took risks and had the budget to realize the risky vision of the filmmaker. In a world starving for new images, Dark City can still provide nourishment.
What's more, it's a movie from a bygone era which holds up to the test of time. The CGI is limited. Almost all of the special effects were practical or done with miniatures and they are still mind-blowing a quarter century later.
It's a movie that has timeless themes which are brilliantly married to a timeless design.
Is it perfect? No. It's damn close as far as I'm concerned. I'm sure that some people will take my recommendation and not like the film. The 75% score on Rotten Tomatoes tells us that one quarter of film critics decided not to recommend it; but, as South Park pointed out, one forth of Americans are retarded.
The only caveat is that you have to stress the importance of watching the director's cut. The theatrical cut is great in and of itself; but, the director's cut is infinitely better.