Barry is my favorite rival. He was motivating, had a good team, and pretty well-developed for a pokemon character. (Not that he had any kind of deep story arc or anything like that, but he wasn't flat. He's a good character.) Some people still don't realize a rival doesn't have to be someone who hates your guts. In fact, I actually preferred the competitive-friendliness with Barry.
While Blue is the classic rival, I have to agree with others saying he gets more hype than he deserves simply because of Gary and nostalgiafags. He wasn't a bad rival at all, though.
I also agree that while the group of friends thing they're doing in the newer games is cool, it's a bit much and I don't prefer it. It often feels unfocused. Though, I think they did a better job balancing it out than in XY than they did BW.
As for Silver, he had good story and development. A good character and the reason I don't like him as much is more personal preference. I also find him to be whiny, and his design isn't fantastic. (again, both of these cons are extremely based on personal preference) However, your rival being Giovanni's son is pretty genius, and the story surrounding it is good too.
Any feedback on my thoughts? I'm glad to see I'm not the only one with Barry as a favorite, at least.