Which enhanced Game Boy Pokémon game gave Pikachu to the player as the only starter?

Pokémon Yellow gave the player Pikachu as the only starter Pokémon.

Released in Japan on September 12, 1998, Pokémon Yellow was an enhanced version of the first-generation games. It was designed to resemble the anime, so Pikachu followed the player in the overworld and displayed a distinctive personality.

Unlike Red, Green, and Blue, Yellow does not let the player choose Bulbasaur, Charmander, or Squirtle at the opening. Instead, those three Pokémon can be obtained later through in-game events, while the rival begins with Eevee.

Pokémon Crystal also enhanced its generation's paired games, but it belongs to Generation II and does not make Pikachu the sole starter. FireRed is a later remake of the original adventure.