According to the people at Rice Digital, many of Namco’s games set in the future, including Galaxian, Galaga, Gaplus, Bosconian, Baraduke, Burning Force, and many more, are all part of a common timeline! Namco calls it the UGSF History. Due to the inclusion of Kissy from Baraduke, which was named to be Susumu “Mr. Driller” Hori’s mother, it also drags in the Mr. Driller games, and even Dig Dug! You can read about it on their site here. Namco’s own site concerning it is here.
According to their timeline, the earliest game chronologically is Ace Combat 3 (which is not an arcade game), and the latest is Galaga ’88!