An arcadey shooter will probably have a single person driving a tank, that suddenly zips and crushes through a flank of enemy troopers. The person then gets off the tank, runs straightfoward into the enemy base with guns and rockets blazing. The person clears a battlion of people with a grenade and continue to run in. The person then deactivates all control panel, plants the bomb on the target, runs away, and watches in a distant as a glorious explosion flattens the enemy base. the person's buddies congragulates him for his job well done, and the person soon gets extracted from a helicopter.

Ok, I'll leave a few words...about what happens if realism was added into a first person shooter yet does not mar its gameplay

(Note: some of these are focused on multiplayer games)

1-eliminate extra Head Up Displays and Crosshair

2-people does not glitch in and out of a drivable vehicle

3-5 man crew for a large gunship or tank

4-gun model in first person is rendered completely in real-time and in game, and moves around depending on what action is being done (e.g. a running soldier has his rifle holstered, rather than appearing on the lower left corner all the time)

5-people react to situations but is still workable (e.g. a tired soldier needs some rest but still can shoot his/her rifle)

6-realistic weapon physics (e.g. the need to crouch and aim in order to fire a rocket launcer, and make bullet drop for ammos. Some BIG RIGS physics would be welcome as it's WINNER!)

7-dead body stays in place and can not be revived

8-people don't just go around going Rambo. (e.g. a group of soldiers are requested by their officers to stay in a barricaded roof to provide covering fire for their vehicles below)

9-less draw distance, larger gameplay area (e.g. Operation Flashpoint)

10-if respawning, people respawn inside a solid base and buy/sell/get/research weapons and technologies. (Inspired by Power Struggle of the game Crysis)

11-no more than 30 kills in a regular round of game 

...