Alright, I'll give my opinion on the rivals because why not?
Blue: He fits the true definition of a rival here. He is directly competing with you to complete the gym challenge to become Champion and the Pokédex for Professor Oak. He is also the best battler compared to the other rivals by far, as he has the toughest AI, high leveled teams, the only one to become Champion thus far, and actually uses a team that would be really good competitively in real life. 10/10 (Very good competitive rivalry with teasing and a challenging team)
Silver: He is directly competing with you to become the world's strongest trainer. Unlike Blue, a childhood friend of yours that happens to start teasing you because of his competitive nature, Silver isn't your friend at all and clearly has issues because of his relationship with his father. I believe that he is a great rival because of this aspect of his character and his character development to become a better person near the end of the journey. His team was above average as well, but not great. 8/10 (Made it clear that it wasn't your friend and was like a secondary antagonist).
Brendan/May: Technically, I wouldn't say that they fit the true definition of a rival because they're not directly competing with you to either become Champion or the strongest trainer. Instead, I would say that they serve as each other's love interest in a way, which introduced a different dynamic to "rivals." I liked them because I thought the support they had for you was cute and is perhaps the only instance of the main character having something similar to a love interest. They didn't have the best teams or highest levels, but the aspect of their relationship was what was great for me. 9/10 (Because of the cuteness)
Wally: Ironically, Wally might actually be the only one in the generation 3 games and their remakes that truly fits the definition of a rival because he directly competes with you to challenge the gyms and become Champion, but of course, you happen to crush his dreams after defeating him in Victory Road. Wally also surprisingly has a strong team in post-game and would actually be pretty good competitively. 7/10 (A great story of overcoming obstacles, but he didn't appear too often).
Barry: A childhood friend of yours, but also, a true rival that directly competes with your character to become the strongest trainer, I personally found him a bit annoying because of his hyperactive personality and him always triggering some sort of cutscene after reaching a new city. Nonetheless, near the end, he had a really high-level team and one that was well-structured. 6/10 (Very strong trainer, but kind of annoying).
Bianca/Cheren: I found this aspect of "rivalry" extremely interesting because the generation V games created the illusion of traveling with your best childhood friends. However, based on the definition of rival, I would mostly consider Cheren to be a rival of yours because he too is attempting to become the strongest trainer, often challenges you to prove his strength, and gets upset when he loses. While I don't think they were the greatest battlers with the greatest teams, I loved the idea of the main character traveling with friends. 10/10 (Because of the friendship)
Hugh: Hugh definitely does not fit the definition of a true rival to me, as he doesn't compete with you at all for anything. In fact, I would consider Hugh more of a tag team partner of yours than a true rival, as he often finds himself battling with you more than against you. Whenever he does battle you, it is always to test you to help you complete your goal. His main goal is to look out for his little sister and get her Purriloin back that Team Plasma stole a while ago. He was relentless in his quest to look out for his sister and is a great friend to your character, as he helps you just the same. He has that big brother instinct. 10/10 (Because of the friendship and his sheer determination).
Calem/Sarena: What I enjoy about the rivals in generation 6 is that it took the idea of traveling with your friends and expanded upon it, which I love. What I loved about this is that not only did it feel like I was traveling with friends in a way, but it also felt like I was part of a friend circle in game. Calem or Sarena definitely felt more like a traditional rival compared to the others, as they wanted to become the strongest trainer and often challenge you to prove it. Like Cheren, they would also get pretty upset if they lose. However, neither one of them had the most powerful teams though. 10/10 (When including them all and considering the friend circle. Otherwise for just Calem/Serena, 8/10).
Hau: Hau is definitely a good friend of yours throughout the game and is a very likable character. He does directly compete with you to complete the Island Challenge, making him a true rival too. One interesting thing about this rivalry is that it seems be an inverse of the Red/Blue rivalry. Much like how you have the Pokémon with the type disadvantage to Blue and he is always one step ahead of you, Hau has the type disadvantage to you and you're always one-step ahead of him. Also, like how you as Red challenge Blue for the championship after he beats the Elite Four, Hau challenges you for the championship after you become the first Champion. Unlike Red however, he ultimately loses to you. His team, however, isn't exactly the best. I also wasn't a big fan of the fact that I often felt sorry for him after beating him so many times. 7/10 (Great friend and traveling companion, but was often too down on himself after losing).
Hop: Hop seemed to combine elements of Hau and Hugh, serving as both a best friend rival and a tag team partner in many instances. He also undergoes a lot of character development after he loses to Bede, where he becomes more humble. Hop is also the only main rival that acquires a legendary Pokémon through the main story, which might potentially make him the most powerful rival if he ever took becoming Champion more seriously with his legendary Pokémon. However, I wasn't a big fan of the fact that he was often a downer. Much like Hau, every time I defeated him, I felt sorry for him. His team also wasn't that good and I don't know if it was because of my play-style, but I thought his team was really underleveled as well. 6/10 (Great friend like Hau, but also like Hau, he was even worse when it came to losing).
Bede: Even though he might not be the main rival, he definitely qualifies as a true rival because he directly competes with the player to become Pokemon League Champion. He also was a throwback type of a rival, as he is one that isn't friendly with you and often disrespects you, similar to Silver in many ways. However, he does undergo character development somewhat after he gets kicked out of the Gym Challenge. I really liked him as a rival and thought he had a lot of character. 8/10 (Great callback to the old school disrespectful rivals).
