Biniku no Kaori is one of Elf's best NTR themed VNs, though for pure Netorare it's more or less unanimous here that their later game
Boku no Kanojo wa Gatenkei is their NTR opus. Also known as one of the best NTR eroge of all time. Marina is getting a lot of love these days, but that it pretty much pure Netorase as good as it is. Gatenkei on the other hand is a proper netorare game and is much more involved.
Triangle Blue is great too, but is actually harder to get to the NTR routes since it was originally a more vanilla VN which they added netorare routes to and re-released, though it was very well done. It still detracts a little from the NTR experience when you actually have to make sure you make the wrong choices if you want to get the NTR route.
Boku no Kanojo wa Gatenkei is your first option for a great NTR story with "good story, character, uniqueness of the VN compared to others. Good art would be nice too." all in spades.
We only get games that good once in a blue moon.