i'm in your conscience
There's nothing in FRLG I particularly enjoyed to train like I do with RSE, but I usually found myself gravitating to Charmander. I hate to sound like one of those crazy Charizard people, but it's just a fun Pokemon to train and I can end up with some unique movesets for it, unlike with the other two starters.
Dragonite and Jolteon are pretty nice too, though! And I don't mind Butterfree either, despite being weak. I've made it work rather well in the past though.