For this top five, rather than parse through his vast filmography, I picked from 13 features he either directed or codirected between 1920 and 1929. You can see my favorites below.
5. College (1927) I realize this is isn't one of his most revered works, but there are plenty of enchanting moments to be found here. It's his most audience-friendly film, filled with the sort of gasp-worthy stunts that made him famous. But it's the final sequence, full of black humor and deep humanist truths, that gives the film its emotional weight. It's the rare sort of ending that recasts all the preceding action in a brand new light.
4. Seven Chances (1925) Said to be the director's least favorite of his own work, the film's offbeat sexual energy and abstract comedy make it one of his most novel, an oddly subversive look into marriage and ambition. The lunatic climax is rightly considered among the crown jewels of Keaton's comedic set pieces, a stunningly orchestrated live-action cartoon sequence that doubles as a metaphor for unhinged feminine rage.
3. Steamboat Bill Jr. (1928) Like College, this is considered a minor work, though I tend to think of it as his last great film. His slapstick is particularly nuanced here, deepening the story's classic romanticism, and he isn't afraid to stick to a certain bit or idea longer than is expected. The film's refined style is what alienates the casual viewer, whereas those attuned to Keaton's sensibilities enjoy its aerated moods.
2. Sherlock, Jr. (1924) A major accomplishment. Instinctively, Keaton understood cinema's dreamlike nature, and explains it to great philosophical and comedic lengths in this quick little masterpiece. The ingenious special effects are fine technical accomplishments, but they're also little nuggets of film wisdom, illuminating wondrous truths about the medium. Keaton shows us how the process of creating cinema and the experience of watching cinema aren't inextricably linked.
1. The General (1927) The film most consider Keaton's masterpiece, and for good reason. It's the one I most often return to, mainly because all of his greatest traits are on display: his artful merging of pathos and kinetic action, his "man-on-a-mission" narrative design, physical obstacles as playful metaphors, and so forth. The physical obstacles are, of course, presented by the locomotive referenced in the title, one of the all-time great movie characters, human or otherwise.