Setting, plot, choice of characters, depth of characterisation, message: a five dimensional space. Thus go the elements of the novel.
In a recent BBC interview, Iain Banks explained that he always starts with plot; other authors (Henry James comes to mind) imagine a bunch of interesting characters in a setting and claim to let things work themselves out.
The famous French novel Madame Bovary was renowned in its time for its treatment of the hypocrisy of the nascent french rural bourgeoisie - namely its message. Now we read it for its timeless characterisation of the flibbertigibbet Emma B.
Every writer wants to craft an eternal classic. The secret seems to be some combination of a message which soars above the merely conjunctural and parochial, real people in an interesting situation, an interesting story to tell and the author has to actually care about the intent of the book.
Add in a deep writing talent and you're in with a chance :-).