My favorite is Lance from G/S/C and HG/SS. He has one of the Pokemon Lineups that I have ever seen, they aren't just cool Pokemon, but they are strong as well making for a tough battle. He also is in the story as he helps you defeat Team Rocket and talks to you throughout your journey.
Lance. First off, in Generation I, Dragon Pokemon were scarce and Ice type Pokemon weren't heavily influenced as they are in today's Pokemon games. With these two factors in mind, it was very difficult to take down Lance from the Elite Four. Now I know he wasn't the champion in gen I, just emphasizing that fact.
I like Blue. Why not? I love to hate him yet admire him for his style (I'm way better than you! ) and he just has a good (yet jerky) feel to him.
Alder was kind, always questioning Cheren (I got quite a kick out of, "I want to be strong!" "But why?" "I dunno!")
But overall, my favorite is Cynthia. She is mysterious, yet classy, and her Garchomp feuds with my Empoleon. She surprised me in B/W (That's what I get for exploring!) and she has a MILOTIC!! <3