Pokémon in Greater China is officially called 精靈寶可夢, or 'Jingling Baokemeng' in Mandarin (Jingling means “spirit” or “elf,” and Baokemeng is a transliteration of Pokémon).
Pikachu was originally translated as 比卡超 (Bei-kaa-chyu) in Hong Kong. Now it is named 皮卡丘 (Pikaqiu). While the name 皮卡丘 in Mandarin sounds similar to the global name Pikachu (as it was always called in China and Taiwan), it reads as Pei-kaa-jau in Cantonese.
"Pokémon Go" is currently the most popular mobile game in the world. China is the largest mobile gaming market, and the most populous country on Earth. However, the most popular mobile game in the world isn't available in China. Check out why at Businessinsider.com.