I think most of the time it either reinforces bad habits, or at best just doesn't help.
The games just arent that realistic. Someone could be hiding behind a regular wall, and rounds wouldn't go through. In real life, unless that wall was fortified, pretty much anything would go through. Players would be killed by a 9mm to the body, yet a person might not die when hit by .50bmg. Never had to account for bullet drop at any range, nor was there any deflection when shooting through glass, even at extreme angles.
Occasionally you can play online with people where you can use actual sound tactics, and those tactics can be rewarded, but that doesn't make it any more realistic.
I used to play Rainbow Six and Rogue Spear on a team. The small team we had worked similar to how a fireteam would work. One of us (usually me) had a full-auto laying covering fire, allowing my teammates to flank the opponents. We used cover, kept distance from each other (so one grenade, or some quick shooting wouldn't take out multiple of us), used a rear guard when there was a possiblity of our enemy coming up from behind.
When we first started there was 3 of us, and we would regularly take on 8-12 other players, and we had a high win %, probably 80-90%.
That doensn't meen that any of us would survive a real tactical encounter. It just meant that our tactics work well for the game. At the same time, there were very poor tactics that were rewarded.
I.G.B.