There are plenty of classics that are infinitely dull; for instance, Camus could perhaps be the only writer to make a plague tedious, and I would rather stick a rusted fork in my eye than read Jane Austen or Thomas Hardy ever again (Jude was obscure for a reason!).
But I love the long novels of Victor Hugo, Tolstoy and Umberto Eco. I even enjoy James Joyce (but Joyce requires more research than actual reading, honestly, particularly in the case of
Finnegan's Wake and
Ulysses).
It is all a matter of preference, really. There are those readers who agree with me, and those with no evident taste.