No not all games have cocktail mode. Not sure about choplifter, but Ms Pac does.
If you press tab while in the game, a menu will come up.
Select Dip Switches.
If there is a cab type option, change it from upright to cocktail.
Escape back to first menu and select reset game.
When you start a two player game it should flip back and forth in between players in cocktail arcade fashion.
I have seen games that have the cocktail dipswitch but still don't flip.(They also didn't have the mame disclaimer of cocktail mode is not supported.)