I don't understand how people say that Blue was easy. ALL of the rivals are easy now that I'm 21 and have the mental capacity to plan ahead and use good strategy. Pokemon games in general are easy now for the same reason. I'm sure I would have had just as many problems with Cheren in BW as I did with Blue if I was still 6 years old. So difficulty had no factor in my decision; Blue is my favorite rival.
I voted Brendan/May because they are pitiful in that they don't even show you their 3rd starter evolutions.
Altough I have to say that, in terms of attitude, Barry is the most annoying rival ever, strong team or not. Those old-school rivals at least kept their insults and bickering short, but Barry talks way too much. And he's too hyper.
Pretty much this. Wally was the rival. Wally was the story of the sick kid who caught his first Pokemon with you, went down your path, overcame health issues and finally tried to achieve his dream.
With confidence after nearly dying, he challenges you to finally test his strength before the Chapionship...And you destroy his dreams quite neatly.
But he doesn't give up. He's determined to spend as long as it takes training on that road, battling you on occasion, until his Pokemon are strong enough to help him reach his dream.
N does the same thing in a way. He's against your character in a more subtle way, but he rivals you, and he knows it. That's also why you fight him near the end of the game, much after you fight Cheren and Bianca.
Cheren and Bianca and May/Brenden were just there to help your character out a few times, but they weren't really interested as much in the end goals of Champion as you were. Wally, however, wanted to become Champion and N wanted...well you know if you played. Technically, N was the Champion, like Blue. So, yeah. They may not of been the conventional childhood friend rivals, but they're the actual rivals for sure.
Oh, shoot! I completely forgot about Wally! Wally was great! Having not played Gen 5, Wally was the only rival, apart from Blue, who I actually liked. Those two were basically the yin and yang of competent rivals.