I've wanted to do something like this for a while. Ever since I became a serious movie watcher some 15 years ago, I've been pretty fascinated about the different expectations and standards people have for the medium. For anyone who doesn't know my background, I lived and breathed movies for my high school years before majoring in Cinema Studies at New York University. I wanted to be a film critic, but I couldn't afford to keep living in the city after graduation and even in an environment like that, the jobs are slim. I did write movie reviews for my hometown paper for a number of years but eventually moved on to other pursuits. I still watch movies constantly, however, and perhaps one day I'll find a major use for this expertise. So long story short, I've had extensive experience with all of these "types" and I'm not talking out of my bum. With that established, let's get started.
For these people, movies just aren't a significant part of life. They've seen plenty, although they would have no clue how many if you asked them. They probably are in a movie theater less than five times a year, for major blockbusters or romantic comedies, depending on taste. Perhaps a book they really liked was adapted into a film, they'll check that out. If they have children, they are actually fairly knowledgeable about the Disney and Pixar canon because it's an easy way to give the rugrats something to do. Learning about the history of movies is not something they have any interest in doing. Chances are they haven't seen most of the more famous classics (i.e. Citizen Kane, Casablanca, The Godfather, etc) unless one was shown to them in a classroom.
It will be very hard to write this paragraph without being condescending, but please know I'm trying my best. A defining trait of the casual viewer is a lack of expectations. They go to movies expecting a two-hour distraction and if they got that, then they're satisfied and it's time to go back to the real world. Every so often, this total lack of critical evaluation can be infuriating to anyone who has thought seriously about film. In particular, Michael Bay's Transformers movies have become notorious for drawing the battle lines between casual moviegoers and everyone else. You'll often hear them defended as "just a dumb action movie" or "a fun popcorn movie," which is a phrase the person saw in an article recently. Perhaps you'll be told to go watch some highbrow French film instead, as if there's no possibility for an intelligent action film. Therein lies the key issue, actually - understanding the difference between "silly" and "brainless." A silly movie can be a lot of fun, but a brainless movie just sucks. I'm not really comfortable calling anything "objectively" terrible, but those Transformers movies really tempt me.
Casual viewers hate the Oscars because... "Who cares about the Oscars? Nobody's ever heard of the movies that get awards!"
For fanboys (hopefully the inclusion of all genders is understood at this point), it's less about movies and more about geek-friendly genres of fiction like science-fiction, superheroes, fantasy, animation and horror. Most of them don't have much interest in the world of cinema outside these genres, but they are incredibly passionate about the movies within their realm. These are the costumed fans who will stand in line at Comic-Con for six hours to watch a two minute clip of the next Marvel movie. When it comes to the movies they love, they are tireless advocates. In particular, fanboys have been essential to the continued success of the horror genre.
However, there are dark sides to this level of fandom. They don't react kindly to innovation or experimentation when a movie adapts their treasured source material. They expect the movie adaptations to cater totally to them and resent attempts to appeal to a wider audience by altering the original stories. When this happens, they flood the internet with the level of vitriol you would expect from gun control debates on Facebook. Tread carefully before you start a conversation about George Lucas.
Fanboys hate the Oscars because...all their favorite genres routinely go ignored by the Academy. The only horror film to win Best Picture is The Silence of the Lambs, which people try to separate from horror by calling it a "psychological thriller." Please. A guy gets his a chunk of his face bitten off, it's a horror film. There you go, fanboys. Don't said I never did anything for ya.
A film buff will watch just about anything because they love movies. They seek a broad understanding of the medium, watching stuff from all genres and locations, and like to share their passion with others. When they see something great, they will sing its praises to their friends. When they see a fun bad movie (i.e. Plan 9 From Outer Space, Troll 2, The Room), they will make sure their friends get a chance to experience it. When they see a movie that's just plain bad, they will relish the chance to rip it apart. If you want a movie recommendation, find a film buff. If they know you well, they'll be able to cherry-pick their mental library for something you will like.
Passion and knowledge of film can impress other people, but it can also cost them friends if they don't keep their ego in check. Some film buffs take a fanboy attitude towards cinema as a whole, dismissing the opinions of others who haven't seen as many films as they have. A long movie-watching resume does give you a very informed opinion, but it doesn't take away the inherent subjectivity of the medium.
Film buffs hate the Oscars because...actually, they are the ones who are most likely to get at least some enjoyment out of it. Chances are, they like at least one of the movies that gets a statue. But they are also very familiar with all the films in each category, getting pissed off about their favored film losing the Cinematography Oscar while their friends are bewildered. It's a serious love/hate situation.
The cinephile is more interested in movies as art than as entertainment. Unlike the film buff, who seeks familiarity with all genres, the cinephile has no use for movies with overt commercial intentions. They have discerning taste and usually have a formal education in the history and language of film to back it up. I once heard a cinephile define "film buff" as "someone who dominates at Trivial Pursuit but has never seen a Victor Erice film." Directors like Erice, Eric Rohmer, Andrei Tarkovsky and Yasujiro Ozu are their bread and butter. They have a huge tolerance for boredom as long as the film they're watching is technically or thematically appealing to them. As you might have guessed by now, there is a noted correlation between cinephilia and hipsterism.
Like film buffs, a cinephile's worst enemy is his own ego. If they can keep that in check, cinephiles make outstanding professors and can get others to appreciate film in exciting new ways. If not, they run the risk of being utterly insufferable like the infamous commentator Armond White. In fact, most film critics are cinephiles (although the late Roger Ebert was definitely a film buff).
Cinephiles hate the Oscars because...they pretend not to care about the Oscars at all. But they do. However, the movies they love are almost always too obscure to get any nominations. Maybe in the Foreign Language category if they're lucky.
As for me, I'd identify myself as a film buff, but I do have a cinephile's education and a few of those tendencies (I have seen a film by Victor Erice, in fact). Not everyone will neatly fit into these categories, but I think articulating differences like this helps create more of a vocabulary that can be useful for discussing movies in general. I'd love to hear feedback about this one if anyone reads it. Am I on to something here or not even close? Which one are you?