She's somewhat plain. Brock is the first Gym Leader you fight and was also a main character in the anime. Misty was a tomboy and also a main character in the anime. Lt. Surge was an American soldier who spoke in broken mix of Japanese and English. His appearance and battle in the anime was also an iconic episode. Sabrina had a neat teleportation Gym, whip, distant personality, and was also memorable in the anime. Blaine is a hotheaded quiz master scientist that received a visual revamp at some point. Giovanni is battled multiple times throughout the game and is prominent in most mediums in which he appears. He's also the final Gym Leader in Kanto.
Erika and Koga are perhaps the least developed Gym Leaders. Koga would go on to become an Elite Four member and have his daughter take over his Gym, but his poison ninja schtick isn't truly exciting. Erika is always sleepy and doesn't really change between games. Her anime depiction was like a character of the day.
