Carly Rae Jepsen and Owl City are the two most straightforward examples that I can think of. The former only has one real hit with "Call Me Maybe" (and possibly "Good Time", actually featuring Owl City), but E-MO-TION is one of the best pop album ever produced and imo the second best in the 2000s/2010s. Owl City has some pretty decent songs outside of the borderline overplayed "Fireflies", if you're into that borderline saccharine pop (which I can jell with). There's a lot of singer/songwriters that only have one song chart well enough to be a hit, like Tristan Prettyman and Vanessa Carlton, that have some decent songs outside of "My Oh My" and "A Thousand Miles".
Outside of that, there's some bands/artists that can technically be described as a "one-hit wonder", even though they're a huge name in their respective scene. Stuff like Incubus, System of a Down, Dream Theater, Dragonforce dcTalk, Rush, ELP, The Mars Volta, Meshuggah, Avenged Sevenfold (actually have never went beyond #51 on the Hot 100), Seether, Apocalyptica, etc. etc. They all have a lot of really good songs, but only one or two have ever made the charts or are played much more often than any others. And then there's regional stuff too. ABBA is a one-hit wonder here in the states, but in Europe they're probably one of the biggest pop acts in history. And don't even get me started on classical music.