If GG had more peripheral skills and/or a better physical profile I'd be convinced. While I don't buy into the shot creation stuff that makes everyone believe he has "talent", he does have potential there. Even if he was awful at it, he does show potential there just by the virtue of doing it. Kind of like a three point shooter who has a low percentage but decent # of attempts is a more promising shooter than someone who never shot the ball at all. There are guys who have skills that they weren't allowed to show, but if they didn't show it in college chances are because they aren't good at it. I think GG could do some damage as a spot shooter/attacking closeouts with his quick feet. That's where I see the most potential.
But even if you buy into his potential as a scorer, he is so bad at the other parts of the game. His playmaking and defense were non existent. He has a terrible BBIQ and effort level. I know he had a better reputation for this stuff in HS, but I still think it's a mistake to overlook that stuff and just assume it's good. Scoring is not the only thing that comprises talent. Anthony Black is not a better scorer than Nick Smith Jr but that does not mean he is less talented. Even though GG was bad at self created scoring, I can see why you might still consider him one of the more talented/promising shot creators....but even if you give him that I'm having a hard time classifying him as the extraordinary talent when considering him as an overall player. I think GG's scoring ability is being highly overrated, but that's not the only reason I'm low on him. It's because the rest of his game outside of scoring looks very bad as well. I don't have a problem drafting a player with the belief that he will make a big improvement in an area that may be considered a red flag, especially if there are ready made NBA skills/attributes that will get them on the floor. But when there are like 10 red flags and very little things to hang your hat on it's a different story.
About half the guys who get drafted at #16 fail anyways, so I wouldn't be that pissed if we took him. I think much stronger prospects will be available, however, and if you're looking for some who could actually be a self creating bucket getter I agree with
@Handlogten's Heros that you should go for Sensabaugh instead. Despite my concerns, I do think that there's a good chance some team will fall in love with him and would not be shocked if Ainge is the one. He's drafted quite a few guys who fell during their college career. Ziare Williams was drafted 10 after stinking it up at Stanford and I think GG is probably better prospect.