Which 1991 game is described as Street Fighter's best-selling release?

The 1991 game described as Street Fighter’s best-selling release is Street Fighter II.

Developed and published by Capcom for arcades, Street Fighter II was the sequel to the 1987 original. It transformed the series by offering a roster of selectable fighters with different moves, backgrounds, and fighting styles rather than limiting the player to one primary character.

Its success extended beyond arcades. The Super Nintendo version sold more than 6.3 million copies, making it Capcom’s best-selling single software title for many years and one of the most commercially important console conversions of its era. Across versions, the game became one of the best-selling fighting games ever released.

The title also popularized competitive one-on-one play, combos, and the modern fighting-game format. Later editions such as Champion Edition, Hyper Fighting, and Super Street Fighter II expanded the original rather than replacing its central historical importance.