Complex sentence: These two games were launched in Japan on September 18,2010, and added a total of 156 Pokémon to the games (starting with Victini and ending with Genesect).
Split into simpler sentences: These two games were launched in Japan on September 18,2010. This Generation and added A total of 156 Pokémon to the games (starting with Victini and ending with Genesect).