Well, rather technically, THAT IS THEIR PERSONALITY.
Also, I'd really like someone to try and point out how the D/P/P rival is boring. I mean seriously, the main thing most people seem to hate him for is because he "has too much energy" (despite the fact that the trait seems to be genetic, seeing how his father is also rather energetic) and "too nice". Seriously, people don't want a rival to be nice?
Have people forgotten what the word even means anymore?
Rival - definition - a peer that equals or matches your talents and pushes you to be better.
Personality aside, I haven't this way seen RBY/GSC. That being sai I don't agree with your statement for one reason. Its not that people need a mean rival, though that would be awesome. Its more like we were all sorta still noobish back then and felt it difficult to beat them and adapted to their personality. Because of this we downplay our new rivals because in reality they've become weak compared to what are noobish selves remember. As for psuedo-rivals, they are suppose to be lame and friendly. I doubt Blue or Silver is going to randomly give you an item cause he respects you.