No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. The Steam version is estimated at $1.6M — a different platform, not this one.

METAL SLUG 3

“METAL SLUG 3” , the masterpiece in SNK’s emblematic 2D run & gun action shooting game series, still continues to fascinate millions of fans worldwide to this day for its intricate dot-pixel graphics, and simple and intuitive game controls! The most highly praised title in the series among Metal Slug fans for its refined balance and game volume, heads out to the GOG gaming platform! ARCADE MODE (MAIN MISSION) - Play the arcade version of “METAL SLUG 3” from the beginning, and explore 5 immense challenging stages featuring multiple branching paths to explore exciting new areas! Make your way through the deluge of fire and fight off gigantic boss characters! MISSION MODE (STAGE SELECT) - Play your favorite stages at will and train alone or with a brother-in-arms on the missions you have unlocked so far! ONLINE MISSION (ONLINE MULTIPLAYER) - Clear missions with friends far away via Online Co-Op Play. Find a fellow countryman or foreign ally and let the mission begin! SETTINGS - Configure display, control, and language settings. LEADERBOARDS - Check your current rank and score in “METAL SLUG 3” at any time, and compete with other players to become the world's No. 1 soldier!!