There are many books there which aren't really masterpieces.
Are Robert Frost first poems really masterpieces?
Was Conan Doyle a truly great writer?
Anyway, for the 21st century one could list works by Bolaño, Houellebecq, Coetzee, Saramago, Antonio Lobo Antunes, Marquez, Llosa, Pynchon, DeLillo... I am very ignorant here, because there are many authors I haven't read yet, but I've heard many good things about such names as Joshua Cohen, Esterhazy, Krasznahorkai, Peter Nadas, Javier Marias, Elena Ferrante, Dona Tartt, Knausgard...
Keep in mind that many of the best authors of the century have already published their first books, but we haven't heard their names yet. How many people in 1919 had heard of William Carlos Williams, Gertrud Stein?
Now the point where are really agree with you is in poetry and theater, which really seem to have nearly died in the English language. The new formalists seem to me to have been perhaps the last source of vitality. Maybe I am ignorant, however...
What I can say is that in my country - Brazil - poetry is more alive than it used to be, with many poets now going back to formalist training (inspired by a somewhat average poet, Bruno Tolentino, but with some very promising results so far), or to new explorations in free verse which seem to me to be much more interesting than the stuff vers-librists were doing in the 60's-80's. As for me, I intend to play a part in this 'neoclassical' revival, but without forgetting the many things we have learned from modern and contemporary poets, specially from such authors as Pound, Hart Crane, Geoffrey Hill.