I, myself, have no singular definite favorite. I have a few that I like for pure aesthetic value (Dragonair, Gardevoir, Cresselia, Jirachi, etc), but for the most part, and aside from the ones that show up like, ALL the time, whenever you walk around in the grass, I like them all fairly equal. Some Fakemon, I even like better than canon Pokémon...
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)