2001: A Space Odyssey has its fans, but they don't fanboy it up like their Trekkie brethren. No Monopoly 2001 Edition released or limited edition cereal with monolith marshmallows. And as far as we know, no one goes to conventions cosplaying as the HAL 9000. Seriously, how would you even do that? Of course, there is a 2001 wiki and some Reddit threads dedicated to fan theories, because that's how the Internet does.
The film's amassed legions of fans though, mostly people who really like films and those who make them. Steven Spielberg credits the film with changing the form, and George Lucas said the film had a huge impact on him and his work. The late great Roger Ebert, arguably the most famous movie critic of the past century, said, "Alone among science fiction movies, "2001" is not concerned with thrilling us, but with inspiring our awe" (Source). Baby boomers look back nostalgically to the first time they saw the film, and a new generation of fans are still debating whether HAL had a mind, and if so, why he lost it.
The film has also entered pop culture in a huge way. People who have never seen the movie are no doubt already familiar with its most famous scenes and its choice of classical music; both have been parodied and given homage time and again.
Mel Brooks opens his film A History of the World with an homage to 2001's first story section dealing with humanity's hominid ancestors. An episode of Mad Men is titled "The Monolith" and is full of references to 2001 and other Kubrick films, including a monolith stand-in for an elevator. And, of course, The Simpsons did it. The show has spoofed it several times, but one standout includes Homer's massage chair experience turning into the famous Star Gate scene. South Park also got in on the action: the "Trapper Keeper" episode has Kyle shutting down a Trapper Keeper-fused Cartman in a scene similar to HAL's famous death scene.
Can we go on? How about Community, Phineas and Ferb, Charlie and the Chocolate Factory, Dragonball Z, Spongebob Square Pants, and Epic Rap Battles of History. And let's not forget video games, where Portal's GLaDOS is clearly inspired by HAL 9000, with that calm, reasonable voice that it uses while planning your ultimate destruction.
So while it can be difficult to point to certain people and label them fans of 2001, the movie has entered our cultural consciousness to such a degree that we're all really fans one way or another.