Personally I have a soft spot for on rail shooters. Few other games in an arcade make me want to keep putting in tokens as much as one of those. And it feels like you get a good chunk of gameplay between each continue, since you start with a lot of lives.
Metal Slug is always fun as well, but for that one you are expected to die constantly and keep putting in tokens. It eats up your tokens way faster than most other games and I usually don't play it for long.
Also, not sure if it counts, but Air Hockey is always a classic.
Any of the Mario Kart Arcade offerings are always good fun, although they are kind of simplified versions of regular Mario Kart with less interesting track designs, there's just something novel about having a Mario Kart game that you can only play in arcades, and I easily prefer it over other racing games in the arcade since those are usually even more basic.