There is a fine line between video-games teaching tactics and being a helpful training aide, and some horrid, bad-habit inducing nightmare.
A lot of gamers who play, use an erratic style of play, often called "Run and Gun" where the terms "Quick-Scope" and "No-Scope" were coined. Like the video posted earlier of the next Darwin Award Winner, the players will run around the map, pulling up their scope and shooting fast, or not aiming all. Both of these are colloloquially (spelling?) called "Spray and Pray" when used with a full-auto firearm in-game.
This style of gameplay originated somewhere around the time of Couter Strike, another popular game, and Call of Duty. When the Battlefield series came out, it was intended for "more serious" gameplay. Meaning, the Battlefield games were meant to have your team working together to achieve your mission objective. There would be a number of squads per team, consisting of 2-4 players each squad. Each player in a squad would fill a certain role, such as Assault, Engineer, Support, and Recon.
The Assault class consists of a rifle, typically MBR type rifles like the M16, AK's, G3, etc. this class (though changed, then restored in BF3) was assigned Medic duty, reviving and providing first aid to your downed or hurt squadmates or teammates.
The Engineer class is usually equipped with a carbine type rifle such as the M4, AKS-74u, G36C, etc. The primary role for the Engineer class is "Vehicle Management" as I like to call it. This class is also equipped with a vehicle repair device, along with a vehicle destruction device. As you can tell, this glass is mainly used for taking out vehicles.
The Support Class is usually equipped with an LMG type weapon, such as the M249, the M240B, or PKP Pecheneg, etc. The role this class plays is putting the opposing team under suppression (an effect of gameplay that has a debilitating effect on your player) and providing ammunition for your squad or team.
The Recon class is mainly equipped with marksman rifles, such as the SVD, M40A5, SV-98, etc. The primary role of this class is spotting enemies, them being equipped with aerial surveillance devices and motion sensors to assist your team by allowing them to know where the enemy is at. They are able to pick an enemy off at greater distance accurately.
The negatives that Call of Duty has brought over to this type of gameplay (Battlefield) is the "Run and Gunning." this method of gameplay just ruins the game, in it's entertainment level and meaning. If it weren't for these lousy tactics of "Run and Gun," the possibility of Battlefield as a good training aid gets higher. It does help with your reaction time and tactics if you play the game it is meant to be played.
You know you are on a good team when your teammates are storming separate objectives at once, but in a coordinated manner. You are also in an effective squad if the squad has one of each class, or two members running Assault and the other two running Engineer and Support.
The Battlefield 3 game is more about your team accumulating a collective score or destroyed object, and your team can really only win with cooperation. Playing by yourself and not working for your team won't help you win at all.
In Call of Duty, there is none of this. You basically just run around and kill the opposing players, using whatever firearm you choose (some of which are poorly represented). This offers nothing. Each player is typically only concerned with his K/D (Kill/Death) ratio. Some of this has followed over to Battlefield 3, which is unfortunate, because it only detracts from the game.
Sorry for my rant on gameplay, the point I'm trying to get across is that certain games, like Battlefield 3, for instance if given a good team, can teach you a lot. Yes, it isn't a substitute for actual trigger time, but gaming can be useful for something.
