Cheren and Bianca did what ever rival after them did first and best, they stopped giving rivals any real bite (honestly out of all the rivals on Silver is actually an asshole, Blue is just competitive but never malicious, people just mix his personality up with that of Gary..but anyways) and instead make them either way weaker than the MC (Selena/Calem, Wally) or give them goals completely different from becoming champion (Arven, Hugh) so them battling you is more of a gameplay contrivance than them trying to best you.
Cheren and Bianca both had arcs that were basically being forced to accept you can't overcome the godking tier plot armor that is being the main character of a Pokemon game and then figuring out what to do after that, Cheren takes off his smogonfag glasses and becomes a gym leader to teach new trainers how to raise Pokemon, Bianca accepts that battling isn't actually her deal and becomes Juniper's aide. Both struggle with this but come out better for it, and Pokemon then just...repeats the arcs these two characters have over and over again with Hau, Hop, LGPE boy, etc. Since they can't have the rival actually win in any meaningful way, and make any assholish characters rude to everyone BUT the MC (Gladion, Hugh), what's left is these friendly rivals that are just different flavors of Bianca, and all come out way worse because they don't have the luxury of getting a sequel where they're older, hotter and more confident in themselves.
This is why Nemona is such a breath of fresh air, since she's competitive and friendly, but still battle focused like Blue, on top of us possibly not even seeing her full power yet (where's her original team?).
Anyways, if your stick is too far up your ass to consider Cheren and Bianca rivals, despite other rivals pre Gen 5 being just as, if not more friendly than them, then N is right there.
