Super Speed Race (Arcade)

According to system16.com, this game was released in Japan in 1977. Midway published it in the US, and the flyer has a 1979 copyright date. Interestingly, the Midway flyer seems to have a painted screenshot where the background looks very similar to the pixel art in the game, but the cars look like incredibly simple compared to the actual game.

According to Masumi Akagi's 2005 reference book

'アーケードTVゲームリスト国内•海外編(1971-2005)'
('Arcade TV game list domestic/overseas edition'),

Super Speed Race 'スーパースピードレース' was released December 1977.

OK, I found a racing game by Taito with color pixel art older than Sega's Monaco GP. It's fun, and the backgrounds look better than the Sega game. The first game in this series was 'Speed Race' from 1974, which also had pixel art (in grey scale).