I did rifle shooting in the past as a sport and achieved higher skill than ~90% of people in my range, able to hit a dime 100% of the time at 50 meters distance - without optics, mind you. Static one though, not moving. But i had my fair share of pistol shooting as well, 25 meters range, both static and moving targets. So i know what you're talking about very well. And i still disagree. Simply because sheer mass of bones, muscles and the weapon itself which are to be moved substantial distance (we talk dozens centimeters here) prevents you from doing it as quickly as you could move a mouse for just ~1 cm to a side (which with right sensitivity is all you need to hit a target to the side in an FPS game). It's not for argument; it's just physics.
But i suspect i know why you think otherwise. You yourself witnessed high enough level of precision and speed of shooting using real firearms. But i suspect you did NOT experience, 1st-hand, comparably high level of precision and speed when doing FPS games - "professionally", if you want to put a label to it. But i did. In early 2000s, i was one of 10 people who won my country's Counter-Strike championship (i was in the reserve 5-man team, and regular sparring partner). I've seen highest levels of precision and speed humans can achieve in FPS games, and at the time, was able to perform at those levels myself, as well. And it's mind-boggling fast and precise. When you're "into" this sort of concentration, time nearly stops and you act so fast others often don't even notice your aim movements. I myself routinely did aimed headshots with a pistol while in the air (mid-jump) so fast that enemies simply failed to react - and those enemies were not some casual gamers, but folks who earned good money outta winning all sorts of regional CS tournaments. Those enemies were folks who refuse to play if latency of local network of the tournament is above 5 ms, or if PCs they play with produce less than 150 FPS (and back then we had LCD displays which were able to actually display that many, of course). They react in ~50...80 ms when "in the mood", by shooting your character in the face, quite precisely, their reflexes are honed that much. And still i developed tactic and skill to take 'em out spmewhat reliably with such headshots, back in the day, jumping outta some corner and feeding 'em lethal headshot before they could react. Means, i was able to 1) see the target, 2) aim the weapon and 3) pull the trigger all in less than ~60ms - doing it with enough precision to land a headshot to human-shaped figure up to few dozen meters away, that is. Never at long range, as CS (back in the day) simply did too much bullet scattering from my favorite USP pistol at longer ranges. Still it was one valuable skill of mine, sure helped our team in tournaments and contributed to shaping everyone up during sparring sessions. Made lots of people furious, too. Good old days...
In other words, mouse allows you to aim and take a good-precision shot in under ~1/20th of a second - if and when you got enough skill for it and FPS game you play is real-time enough (one of most important features of "true" Counter-Strike, which is beta versions 1.6 and lower, - is extremely low delays for everything, with good hardware and LAN it's practically true real-time interaction). And with all due respect to real pistol masters, i simply know they can't do the same that fast. Most of that amount of time, - 1/20th of a second, - will be spent for one's brain processing visual information about target's whereabouts, means less than 1/50th of a second is left for actual mouse / arm movement to aim the weapon and pull the trigger. Muscles, distances and forces involved make it possible to do with a mouse - that fast, - but impossible with any real or light gun. I am sure.
Now what you see in most modern FPS games, both single-player and especially multi-player, - is surely much more sloppy and lagged. What i just described requires special hardware (quite expensive, and properly set up, too - things like more than 0 buffered frames in your GPU will already ruin things much), strictly local network (internet latencies are just too high), people who spent couple years or more to hone their reflexes, training for it on daily basis, to play with - and comparable experience on your own part as well. Any single of those 4 requirements missing will pretty much disable your ability to properly estimate what "good laser mouse" hardware can do. Very few people have ever experienced this, but i did, and i know what i am talking about.
