Most played Coin-op?
For me the easy answer is Ms. Pac-Man. Although A favorite, this was not my #1 favorite game-no, it's just that the machines WERE EVERYWHERE in the early to mid 80's (I last saw one, in fact, in 1999!) ... so I dropped a washington in the slot wherever it was, at grocery stores, laundramats... gad Ms. Pac was EVERYwhere!
The second, runner up, would be the opposite...my fave coin-op, GAUNTLET. It was in a nearby conveiniance store in the mid 80's for about a year-only place I saw one-but I played it to DEATH! I recall walking down to the store at 5 am (when they opened) on freezing cold mornings in January just to play this thing for an hour (Always the Wizard!)...you can imagine how thrilled I was when the official NES version came out and the near perfect Genesis version years later...yet somehow, being able to continue non-stop at home made the game dull. Having to PAY for more health made all the difference!
Others?