Call me a Hypocrite and what not but the best NTR is where YOU do the cucking, and not the mainstream where you see through the eyes of a Beta Semi Protagonist getting his wife/GF/Littlesister(lol like there are) get fucked while he's hiding in a fucking closet or something.
I also agree that Rance is at the Top Echelon when it comes to Main MC VNs
The best NTR would be a mix of both. There are those that have you be the cuck and the one cucking which forces the MC and the player to consider their own actions. This happens to Rance where he cucks and people can in turn, cuck him by raping his girls. The issue I have with Rance is that he's too vanilla now. At his highest point, he was an asshole. He was the kind of MC that represented the worst of the players. His actions were aligned with ours. But his behaviour highlighted how stupid collecting CG of random girls were. It was a great way to show and also make fun of the nice boy heroes in these games as nothing more than hypocritical. But now? His recent games have made him a hollow shell of his former self. It's like alicesoft just decided to embrace the stupidity instead of play with it.
No offense but i don't really agree with you guys about Rance. If Takaaki the protagonist of this game is on the extreme end of the cuck scale then Rance is on the other extreme end, not so much different than a thug. I know these are hentai games but i'd still want someone in the middle ground not extreme like these 2 type as protagonist.
It's hard to make a MC in the middle. It depends on how well you can write them as MC like Rance fits cg collecting games with random girls with a handful of reoccurring female NPC/playable characters, and Takaaki and his ilk fit the VN games where you are pushed down routes for a relatively small number of girls. If you aren't careful, you get a Hamazura. (joke on how much ass pulling Kamachi does for this 3rd protagonist in To Aru Majutsu No Index)
You could say it's an art form. If you are a predator, characters like Rance or males in netori are easier to write as they can be as one sided as possible without compromising on the genre and the themes. If you are trying to court some random girl, Takaaki is much easier as they are rather weak to begin with. They aren't meant to be brimming with personality. This can be seen in Gekkan Shoujo Nozaki. In shoujo dating sims and whatever the opposite for males is called, being a weak-willed yes man makes everything easier.
Really the best way to get a middle ground MC would be games where you play as a female and are given choices for sex. They can be as flat as possible without pushing you down the path of a predator or the prey. Sort of sad really. Why isn't there a netori game involving Kuroko trying to steal Misaka and cuck Touma, only for her to be saved by his chadness. Ending in her cucking Misaka, the one she was originally trying to steal.