Taking a look at the history of pokemon through Gens 1-6, we do get to play as a handful of protagonists! But that's not all, we also get to play as a handful of protagonists from the spin-off games too. Usually in the main series of pokemon games we play as 10 year olds (or around that), while in Black and White, we play as older people. Now, just taking a look at them:
Main Pokemon Games
Gen 1: Red & Leaf
Gen 2: Gold & Krys (Crystal)
Gen 3: Brendan & May
Gen 4: Lucas & Dawn (D/P/Pt) Ethan & Lyra (HG/SS)
Gen 5: Hilbert & Hilda (B/W) Nate & Rosa (B2/W2)
Gen 6: Calem & Serena
The Orre Series (Pokemon Pokémon Colosseum and Pokémon XD: Gale of Darkness)

Wes & Micheal
The Pokémon Trading Card Game series
Mark & Mint
Pokémon Ranger series
Lunick, Solana, Kellyn, Kate, Ben, and Summer
Pokémon Conquest
Hero and Heroine
There are also of course the pokemon mystery dungeon games, where you play as a selection of pokemon (mainly starters), so, if you wanna count that, you can! At any rate,
Which protagonist(s) were your favourite to play out of the bunch here? Why?