Every class at UC Riverside is top-notch (because it's a top-notch university, of course!) but some classes are definitely more popular than others. Intro to Creative Writing, taught by Professor Goldberry Long, is an extremely popular course that I was privilege to take during my first quarter at UCR. In the class, you dive deep into both the mechanics of writing as well as the way that stories can evoke feeling. Goldberry's heart-wrenching stories of her childhood always spark your imagination, leading to pieces of work you never thought you'd be able to write. There are also many obscure courses, like Skepticism & Pseudoscience, "Evil", Food in Film, and even the study of creepy crawly insects in Entomology! The variety of classes at UC Riverside is massive, so you're guaranteed to find something that will tickle your fancy!
I'd call one of the most popular classes Bio30. From what I hear, it is a class about human reproductivity and things dealing with that. It fills up almost immediately. Other than that, it would seem that creative writing and Japanese language classes are very popular, since it is hard to get into them. Though, that is probably because the classes are small and inconveniently uncommon. There are also classes like the psychology of evil and a class on myths and rituals that are popular.
The most popular classes are classes like Intro to Art, Theatre, Drawing, Painting, etc. These "fun" classes tend to be filled up fast since any student can take them and they tend to be easy to pass, an easy "A". The classes that everyone takes however, if that makes them popular, are Introductory level English, History, Sociology, Philosophy, etc. as all students need them for breadth requirements.
The classes that people are always trying to get into but are always full: Psychology 2 (an Intro class that focuses on the abstract vs scientific aspects of Psychology) and the class about sex that counts as a Biology requirement. Creative Writing classes are also always packed because it is an impacted major. Biology and Chemistry classes are also always packed because it is an impacted major.
Popular classes are easy classes. Bio30 is an elective class that most students save till their last year in college (for that easy gpa boost). I took this class my second year at UCR barely going to class and got an A. Just go on ratemyprofessor.com and look up your professors before enrolling in the class to see who's easy.
I think psychology might be one and Language classes. its hard to get the classes you want because there are so little and so many students that you have to make due with what you can get. and i think popularity depends on your major also
To be completely honest, I know a lot of people majoring in Political Science so I hear a lot about everyone taking American Politics, World Politics, and any other political course offered. I'd say those are the most popular courses.
Science classes gets filled up pretty fast. Most people who have late registration appointment don't get in the classes they wish to take.