I find 2D NTR games very enjoyable. Theres just something about the freedom of movement that renpy games just don't have. On that note, the NTRPG games are absolutely a must play. NTRPG 2 is more polished than 1, but they both have things to offer. Hanataka, the author of the games is very talented at building suspense and uses sound design very effectively.
For other recommendations, there is also Amour Maho Academy. That one has a nice and long NTR build-up that makes the experience extended and painful. Lovely. The art is a little iffy, but the arts isn't that important to me in an NTR story. It's not what I look for in those games. I heartily recommend that one.
There also the one by the same creators as Tiina, Until her amorous body corrupts, if you didn't already experience that one. It also has a very good slow burn going for its story, making it a very enjoyable NTR experience.
There are plenty of other 2D NTR games, but as usual, the good ones are in japanese. A while back I found this game that had a couple and "a third wheel" be stranded on an island and while there, the other guy puts his moves on the girl and its all downhill from there for the protagonist. It was honestly what I wished that game Daniels-K made a while back with the similar deserted island NTR setup. And it's all in japanese. Goddamn that setup is just too good. Trapped on an island with your girl and another guy and then watching as that love is stolen away, with nowhere to even escape from the horror of it all. Being forced to hear the debauchery taking place right next to you, but biting your lip in impotent anguish as the last shreds of love your girl had for you turns to disgust. What an absolute nightmare. It's such a perfect NTR setting.
*sigh*
Waiting for those proper japanese NTR games to get a translation can be so painful sometimes, but when one does get translated, oh boy. Those days are special.