The best spy novels are a few decades old now, so they're all bound to be dated. But then I suppose Shakespeare is dated.
John Le Carre, Eric Ambler, Graham Greene, Len Deighton are all high quality, as are Somerset Maugham's Ashenden stories. Though if you're looking for thrills and spills, Maugham is not your man. His work is very character-based.
I wouldn't class Ian Fleming's novels as spy novels: they're too far removed from reality to count as that. But as stylish action thrillers, if you can get past his worst excesses, they can keep you reading.