On Emerald I initially chose Torchic because I'm used to choosing Fire-types. Horrible mistake imo, got bored/sick before beating Norman. I'm much happier now I restarted with Mudkip. My Marshtomp helped crush Wattson :D someone whose gym I somehow struggled with initially.
On FireRed/LeafGreen I chose Charmander, 'cause I just love Charizard. I'll restart eventually starting with Squirtle the Bulbasaur though.