>>4512N was always pretty special, because of the way he's symbolically set up as an opposing force to the player and combined with the role of evil team leader (until the Dennis 'reveal', anyway). So he's pretty much the most important character in the game compared to a usual rival who's secondary.
Since gen 5 they kept repeating the May/Brendan formula of friendly character whose dreams get crushed by your OP-ness but they learn to live with it, with Kieran being the most recent one. Lillie was pretty much N as a waifu but without being a rival or evil team leader, which is why people criticize Gen 7 as a guided tour kek (I still haven't played it myself)
Arven and Nemona were very likable imo and have been well received by most people. Kieran feels like they brought back the old formula but make him go batshit this time like they want to subvert the trope except it ends with him acting mindbroken back into friendship by your OP-ness anyway, so I don't know what happened there. He seemed like a big mess of wasted potential with the way everyone was speculating the evil peach legendary was mind-controlling him only for it to turn out to be a big red herring. I wonder if there were some last-minute rewrites from GF. It's super weird. But N himself has plenty of mysteries like the rubiks cube that was supposed to be plot-important and his planned psychic abilities.