I'm going to be blunt: I hate Cynthia.
I hate that she was given such a blatantly cheap, overpowered "perfect" team. I hate that she was stuffed into every single DS era main series game while other, perfectly good characters were left to rot. I hate that, instead of being a good or even interesting character, she's instead, a bland Mary Sue with perfect supermodel/Barbie doll looks who always says the right things at the right time and doesn't have any flaws. I hate that the fandom blindly worships her and uses her as a stick to beat other Champions with. I hate that both GF and the fandom hold her up as the "ultimate" Strong Female Role Model and use her as a stick to beat other female characters with.
Sure, you could argue that Lance is a Gary Stu, but he actually showed character progression going from RBY to GSC. He went from being a bratty, overconfident Elite Four member:
"Ah! I heard about you, Red! I lead the Elite Four! You can call me Lance the dragon trainer! You know that dragons are mythical Pokémon! They're hard to catch and raise, but their powers are superior! They're virtually indestructible! Well, are you ready to lose? Your League challenge ends with me, Red!"
"That's it! I hate to admit it, but you are a Pokémon master!"
To being a gentle, humble Champion:
"I've been waiting for you. Gold/Kris! I knew that you, with your skills, would eventually reach me here. There's no need for words now. We will battle to determine who is the stronger of the two of us. As the most powerful trainer and as the Pokémon League Champion… I, Lance the dragon master, accept your challenge!"
"…It's over. But it's an odd feeling. I'm not angry that I lost. In fact, I feel happy. Happy that I witnessed the rise of a great new Champion!"
Sure, his team isn't as good as Cynthia's, nor is he anywhere as difficult to battle, but having a tough team doesn't mean jack if there's no character to go along with it...
... which is why Blue is still the best Champion. :P