While I don't claim that everything I read will pass this test, particularly books on my TBRD pile, I do skew towards literary fiction that generally will pass this higher threshold. I've indicated that there are a few key gaps in my reading, particularly the fiction one would read in American lit. in high school (as discussed here) and some gaps in 20th Century literature written in English here.
I have done a fairly good job of filling in the gaps in Russian literature, including essentially all of Dostoevsky and quite a few 20th Century Soviet novelists. The single most notable missing book is Tolstoy's War and Peace, which I have pencilled in for 2018 or so. I also plan to read Turgenev's Smoke and Chekhov's Seven Short Novels, but these probably wouldn't be considered canonical.
I've made some progress in Italian lit. by reading most of Italo Calvino, Goffredo Parise (though I only own and have not read Cesare Pavese) and more recently Gadda's That Awful Mess. I recently picked up Privo Levi's The Periodic Table and hope to read it reasonably soon, and at some point I'll try to get to The Leopard by di Lampedusa.
Probably the most shocking gap is how little French literature I have read. I'm somewhat haphazardly reading Emmanuel Bove and Patrick Modiano (and Némirovsky intermittently), though I am well aware how perverse that is, given what a narrow corner of the French literary establishment they inhabit. I have to admit it wasn't until 2013 that I finally read Madame Bovary, and I finished Proust in 2014, and that was a major accomplishment for me, given how resistant I was to Proust's style and preoccupations. While it is a bit perverse, I will read from the 20th Century on backwards, so Perec and then Camus and Gide and probably Celine and just possibly Sartre and then finally Balzac. I am not sure about Dumas or Hugo. At the moment, I don't intend to get to them, but I may change my mind at some point. So there's a lot of heavy lifting there, but also a lot to look forward to.
I'm also not at all up on German literature, and I probably never will be. I have read a fair bit of Rilke and some key texts by Goethe and Grass's The Tin Drum and Mann's Death in Venice (and pretty much everything by Kafka, though one would hardly consider him a "German" author). That's really all I can recall. I will eventually try to get to Mann's Buddenbrooks and The Magic Mountain (but not Joseph and His Brothers) and Musil's The Man Without Qualities, but I doubt I'll get much further than that. I don't know that I would really consider Fontane canonical any longer, as he seems forgotten (at least to the English-speaking world) but I have a few of his novels including Effi Briest. I'm also slowly working my way through Gregor von Rezzori's work with Memoirs of An Anti-Semite coming up later this year and The Death of My Brother Abel probably the following year.
I expect the core of my reading will remain grounded in English and American novels, from the 1800s onwards. I won't repeat all the books from those other lists here, but some of the top ones I am going to try to read (many of which are already on my main reading list) are here:
Austen Mansfield Park
Bronte Jane Eyre (probably the second most notable omission -- at least I don't recall reading this)
Dickens Oliver Twist
Dickens David Copperfield
Dickens Great Expectations
Gaskell Wives and Daughters
Gaskell North and South
Trollope He Knew He Was Right
Trollope The Way We Live Now
Hawthorne The House of Seven Gables
Thoreau Walden (the entire thing -- I've read several key sections)
Bennett The Old Wives' Tales
Hardy The Mayor of Casterbridge
Hardy The Return of the Native
Hardy Jude the Obscure
James The Wings of the Dove
James Portrait of a Lady
Lawrence Sons and Lovers
Lawrence Lady Chatterley’s Lover
Willa Cather Death Comes for the Archbishop
Wharton The House of Mirth
Fitzgerald This Side of Paradise
Fitzgerald Tender is the Night
Hemingway A Farewell to Arms
Hemingway For Whom the Bell Tolls
Conrad The Secret Agent
Sinclair Lewis Babbitt
Sinclair Lewis Main Street
Steinbeck Of Mice and Men
Steinbeck The Grapes of Wrath
Steinbeck East of Eden
Maugham The Razor's Edge
Koestler Darkness at Noon
Kingley Amis Lucky Jim
Waugh Brideshead Revisited
Lowry Under the Volcano
I'll never be completely satisfied or feel I have read everything that deserves to be read, but getting through my main list -- as well as the ones above and those on the secondary lists scattered throughout this blog -- will be a significant achievement. It's probably doable in the next 10-15 years... In fact, I should get to 8 or so books in the next 12 months, including knocking off the Thackeray. When I get through that, I may well rearrange the list and bring Jane Eyre up next (and its companion Jean Rhys' Wide Sargasso Sea) depending on my mood at the time.