Not to be controversial, but I'm gonna go out on a limb here and say he's my fave champion to date lmfao.
Lance was boring as hell. His generation one team wasn't even a full 6-pokémon roster, and 2 of those 5 pokémon were identical NFEs, easily making him the most pathetic in team building alone. He wasn't much better in generation two, either, with 3 goddamn dragonite. And I know that LGPE only had gen 1 pokémon, but seadra? Really? His design is cool, but for a dragon tamer, he doesn't have an admirable variety of dragons in his championship teams, and he has no personality whatsoever imo. He's just... serious. Congrats, that's boring. Blue/Green was a better, with more variety, but I don't really consider him a champion because he ultimately becomes a gym leader and that final battle is more a rival battle than anything to me.
Steven's team is pathetically easy to beat and again, like Lance, he's... serious. And he likes rocks. His design is pretty good, but design alone doesn't make a champion. Wallace is better in terms of having a personality imo, but again, his championship team is kind of sad and pitiful in terms of how easy it is to beat. I mean, mono water? Really? Bring a grass and electric type (and a flying type for his ludicolo, if you want to be completely set) and you're good.
Cynthia is the first real champion to finally understand the importance of a balanced team (I mean, how are we realistically meant to accept that Steven Stone kept his champion title for so long with such an unbalanced team?), though imo she was nerfed in Platinum when they replaced her gastrodon with a togekiss. Then again, I still never found her especially difficult - just a little more difficult when thinking back on her battle in comparison to the others - and she was my first ever champion, back when I was 5/6 years old. That being said, I know many struggled against her, so her difficulty isn't a hindering point here - people generally found her to be a massive obstacle, and that's a good thing. Her design is brilliant, her music is brilliant, and she has a bit more of a personality, but again... she's still weirdly formal and reserved, given your avatar is meant to be a 10 y/o child. And why does she ask you to deliver her grandma a charm?? What's that about?? Don't get me wrong, though, I love Cynthia. She was my first champ and she'll always have a special place in my heart.
Alder is also rather easy to beat, but he has variety in his team and an actual attempt at a personality, so I can't really complain. His design is... interesting, and he has a sympathetic backstory, as well as an interesting reason for his ascension to champion. Iris, on the other hand, is way more endearing, and her design is brilliant. That being said, I've already established that mostly-mono or unvaried teams aren't exactly difficult, and Iris didn't exactly live up to her appearance and brilliant theme in terms of difficulty. I beat her in my White 2 sololocke (i.e. a nuzlocke but you can only use 1 pokémon - i.e. your starter, which in my case was a samurott that wasn't, for the record, overlevelled) with minimal potions, so I think that says everything about her. Even so, she's one of my fave champions based on design and personality and theme alone.
Diantha had an endearing personality, a brilliant design, a great theme and a terrible team. Really, she let me down. I beat her mega gardevoir with a scrafty that wasn't overlevelled. That shouldn't happen.
Professor Kukui wasn't difficult, but he had one of the best personalities to date imo, and actually was... likeable and frequently present. I didn't enjoy his battle because it was a challenge, necessarily, but because I was caught up in his dreams and was glad that he'd finally managed to fulfil them. Hau, much like Blue/Green, felt more like a rival battle than a champion battle, but I'm one of the people who loved him, even though he also wasn't much of a challenge.
Onto why I like Leon, though, rather than just why the other champions are,,, idk, subpar. Personally, I've never understood why so many champions are able to hide their champion status until you get to the league. I mean, shouldn't the champions be... famous? And well-respected or loved by the population, given how battle-driven the pokémon world is? Why is Cynthia unrecognised until you get to the league? It makes no sense - and then there's Leon, who... is inescapable. He's everywhere. In a region based on Britain (my country) and inspired by football culture, it makes sense that people treat him like a celebrity - and that he has sponsors. I mean, football stars do! That's the point!
And... no offence, but the whole "he likes charizard, is undefeated and often gets lost" shtick is, while mentioned, like, once by Leon himself, actually played up more by the people of Galar, which fits with the annoying habit of fans reducing their fave celebrities/characters down to a handful of uwu traits that suit their personal ideals. Leon himself is shown to be more complex than that: he's observant enough to notice how much Hop has grown exactly in just a glance; he ran after Hop and the protag to protect them in the Slumbering Weald; he repeatedly insists on dealing with danger because children shouldn't be expected to save the world, THANK YOU, LEON; he risks his life to protect Galar from Eternatus, even though he fails; he gives himself 3 days of rest before battling you even though Hop implies he was badly injured by Eternatus, which is... admirable as well as alarming- I could go on and on and on, and I haven't even mentioned the subtleties in his animations, especially when he loses battles. There's lore there, with his distant relationship with his family and his complicated relationship with Chairman Rose and the fact that he's been champion since he was 10, which is... immense pressure in a society like Galar's.
And granted, he's doubled up on the ghost and dragon typings, but by god does he have type coverage in his moves. The amount of times I've seen people online talk about how they sent out a drednaw against his charizard only to have it fall to a max overgrowth is unreal, and to be honest? I actually struggled a bit against him, and I was by no means underlevelled or poorly equipped. Like him or not, he was very easily capable of being a challenge, especially if you weren't expecting him to run max overgrowth. Sure, his battle theme... isn't the best in the franchise, and I massively prefer the battle tower theme in terms of "themes that play when Leon's around,"
Okay, his design is... questionable in terms of, you know, how aesthetically pleasing it is, but it screams "big kid" to me, which makes sense, given his public image/public personality. And as for his apparent perfectionism, how he's never lost a battle and the like... tell me that the protag of every game isn't essentially the same. I know for a fact that I've only ever fully lost maybe five battles at most in a game, and that's only when I'm restricting healing items. It makes sense that a champion would be similarly invincible.
I'll stop rambling now but,, I figured I'd be one of the only people with this viewpoint lmfao so I figured I'd go all out
EDIT: I will say that charizard was a poor ace decision. Not because I hate charizard, but because a champion's ace is traditionally from their generation (with the exception of Diantha, buuuuut mega evolution was a new gimmick, no gen 6 pokémon had them and gardevoir totally isn't overrated /s) and there are so many cool Galarmons to choose from. Still, that aside (and the general lack of galarmons on his team aside), his team is pretty great.