The simulator is great, but the things that make an F1 driver are completely different to what is needed to drive a sim. If you gave alonso the option to exploit and as much practice as he wanted, i'm sure his time would be awesome and perhaps top. But that is not why he is driving for the Top F1 team, that is not why he is 2 times world champion.
You can take all the skill in the world into an F1 car, but without having what it takes, your body will fail, your concentration will lapse, your fear will slow you down. To drive in F1 your body has to be able to take massive forces, punishment and intense heat. You have to be able to keep your concentration focus to the max throughout all this for up to 2 hours in a race, in qualifying you are under pressure to perform on the spot, you can't practice endlessly, you have to nail it first time, and if you dont perform under this pressure, you can lose your job. You have to believe in the car and trust in yourself and your own ability, you have to be confident or you will fail. In a sim you can enter a corner at 200mph, and you have no worries about that, if you crash it doesnt matter. If you crash in real life, you risk your life and wreck a car that is worth millions, but if you fear that, then you will be slow.
The actions of driving a Sim may well be similar or very close to what it takes to drive a real F1 car, but the comparison ends there. Sim racing is a skill of the computer gamer, talented drivers too perhaps, but to actually do it in real life takes so much more.