Yeah Ridge Racer games have a lot of ads and cameos of other Namco games in them. Heck, in Ridge Racer Type 4, there's a whole track named Phantomile, which is the setting of Klonoa!
Another PSOne game that has a Galaxian 3 billboard is Tekken 3. There is an amusement park level with that in the background. Which makes sense, since Galaxian 3 was probably showcased in Namco's indoor amusments parks in Japan around that time.
In Japan, the Galaxian 3 theater arcade game looked way more immersive, with more players and chairs and stuff. In the US, at least the one I played, it was just behind some curtains and four players could stand at the guns and shoot at a big screen. But it was still pretty big for something in an arcade from the early 90s. Now go read my E3 article! :)


