The game I played was Berzerk. The objective of the game was to shoot the robots and exit to other rooms populated with more robots. These robots can be avoided, but shooting/killing them grants you points. Robots can kill you on contact, and there are other robots that can shoot as well. There is also a smiley face that floats around randomly and can’t be shot but can kill you on contact. If you clear all the robots in the current room, the robots in the next room are harder to beat.
I think the main difference I felt between the emulator and arcade cabinet was the reliability and the convenience of the controls. Playing on an emulator on a laptop, the controls (keyboard) are not likely to get jammed or only work in specific angles. With the original hardware, controls might only work half the time or the shooting button only works if you smack the arcade cabinet on the right two times. I think the controls are more convenient too. I imagine this game would have a joystick for direction and a button for shooting. Moving a joystick takes longer than pressing arrow keys, but the single button to shoot is essentially the same.