Colorful, dramatic, large-scale science fiction adventure, competently and sometimes beautifully written, usually focused on a sympathetic, heroic central character and plot action, and usually set in the relatively distant future, and in space or on other worlds, often but not always optimistic in tone. It often deals with war, piracy, military virtues, and very large-scale action, large stakes...The problem, of course, is that so much fits into this definition. To avoid that, I will put emphasis on "very large-scale action" and take that to mean "multi-planetary action."
Since I mostly teach American literature courses right now, I'm going to make two lists -- one for an American literature course and one for a British literature course. However, I am also wide open to the possibility of a World Lit-style course, so if you have suggestions for space operas written by people outside the traditional science fiction zones, please suggest them in the comments.
American Space Operas
The Skylark of Space by E. E. Doc Smith (1946)
Foundation by Isaac Asimov (1951)
Starship Troopers by Robert Heinlein (1959)
Ringworld by Larry Niven (1970)
Shards of Honor by Lois McMaster Bujold
Ragamuffin by Tobias S. Buckell (2007)
Dust by Elizabeth Bear (2007)
The January Dancer by Michael Flynn (2008)
British Space Operas
Rendezvous With Rama by Arthur C. Clarke (1972)
Canapus in Argos by Doris Lessing (1979-1983)(not sure which book I'd pick)
Consider Phlebus by Iain M. Banks (1987)
The Reality Dysfunction by Peter F. Hamilton (1996)
Revelation Space by Alastair Reynolds (2000)
Light by M. John Harrison (2002)
Singularity Sky by Charles Stross (2003)
Natural History by Justina Robson (2004)
Of course, teaching all of these books in a single semester might be difficult. Sacrifices suck... I've also not included short stories, which are likely to replace certain novels (such as Bujold, who has written many shorts in the Vorkosigan Saga, thus opening up space for more space operas).
So, what would you change in my lists? What am I missing?
Note: I am not pleased by the overwhelming number of men on my lists. Due to my definition, many of my favorite female authors simply didn't fit, which exposed a critical gap in my reading. If you have recommendations for significant space operas written by American and British women (other than the ones I've already named), please let me know so I can start filling those gaps in my reading.