Green is putting up 14/4/2 per 36, which is good for a spot-up shooter who's only facilitative responsibilities involve making entry passes. He definitely could fail in another system, but I don't think he'd have to get Hill's assist numbers to be as good as Hill.
A lot of that comes from positional differences. Green is the more diverse defender. He's able to guard three (sometimes four) positions. Hill could barely manage two-guards (which is fine, since he should only have to guard points with George next to him). By that same token, Hill's position has forced him to take on a bigger role in the Pacer's offense. He HAS to get the assists, because that's his job as a point-guard. As a shooting-guard, Green doesn't have to (which is great, because his ball-handling would probably prevent it). Both of their strengths and short-comings are affected by their position, so it's hard to directly compare them.