Since Giovanni isn't a Gym Leader anymore (the manga he gave that up for being a Rocket and the Spoilers say Agatha is the Viridian GL) and Brock left it to his father and brother in the special episodes, I still stand by my statements but yeah, it's just not many candidates are worthy of this title.
So fine, I'll make substitutes.
I'll say James as one. He's knowledgable about Pokemon and it's obvious he cares about his Pokemon (although I do question Chimecho and their bond at times, wasn't as cute as Victreebel or Cacnea). If it wasn't for the Rockets' influence, I think he could easily go the GL motions and could compensate for his losing streak as he has that determination (400+ episodes of wanting to catch Pikachu would obviously mean he has the nerve to win).
He would use his head and his heart, when apropos.
I'll think of the other one when I get more of my wits about me.