I would second the Cal Club and Monterey Peninsula CC, neither of which were all that exciting "before".
Atlantic City CC was better than those two "before", so I don't think the improvement is nearly as dramatic. And I wouldn't rate it as highly now as those other two. But, it's way better than Eugene CC, which is one of the most overrated courses I've seen.
Y'all are just not thinking back far enough. Royal Melbourne is a redesign ... and an unbelievable one. Muirfield is 100% better today than it was in 1919. Lahinch -- by MacKenzie's redesign. But, all of those were pretty basic courses at one point, that hadn't had a lot of money or a lot of architectural thought put into them until Colt or MacKenzie came along. It ought to be harder to improve a course that much today, because in theory, most of them have been able to afford decent architectural input before.