Without McQuarrie, there wouldn't be a Darth Vader helmet, or a Boba Fett suit, or Storm Trooper armor, which means you would have spent an entire decade of your childhood dressing up each Halloween as a ghost or a skeleton or some bullshit. Unless you did do that, in which case, you should watch Star Wars, it's really good.
McQuarrie didn't just work on Star Wars. He also designed the mother ships for both Close Encounters of the Third Kind and E.T. You can even see some of his original drawings in the movie Raiders of the Lost Ark when Indiana Jones shows everyone the devastation the ark is capable of inflicting.
The Bible wishes it was illustrated by McQuarrie.
In other words, from the time you were old enough to make gun fingers until you hit puberty, just about every one of your fantasies took place inside of a world designed by McQuarrie.