Gardner was selected to be the Green Lantern of Sector 2814 (Earth's sector) by alien Abin Sur's power ring, but Sur's ship was on a crash course and he needed to find someone closer to the crash site. Because of that, Abin Sur selected Hal Jordan over Gardner. Not long after, Jordan was made aware of Guy Gardner's existence, and extended an offer to the somewhat obnoxious hothead to take on the mantle of Green Lantern.
Back in the 90's when I would spitball Green Lantern casting with my friends, there were two actors that were right for the part, in completely different ways. David Caruso would've been a great fit as Guy Gardner. He's full of tough guy swagger and sports a brusque, unapproachable persona to go with his naturally red hair. Denis Leary was my favorite dream choice for the role, though. It's a shame Leary is too old for the part. He could've captured Gardner's hilarious abrasiveness perfectly, the Green Lantern we hate to love. He can also play tough, while staying funny.
Scott is quite different from both Caruso and Leary, but he certainly fits in with the age of the Ryan Reynolds Lantern. Imagine American Pie's Stifler as a superhero, and you're on the right track. Scott would be hilarious in the part, and if you don't think Scott has the physique to play a superhero, then you haven't seen Scott with his shirt off. He gives Reynolds' abs a run for their money.
What do you think about appearing in Green Lantern 2, Guy Gardner?