I agree with a lot of what has been said here so far. In terms of innovation and competition, the MTH era is probably the defining factor. I am glad I got to experience at least the last half of the era, with the OGR York bus tours to MTH, Weaver, Tony Lash's layout and Bob Weaver's layout being highlights of my personal experiences.
That being said, personal perceptions of a "Golden Age" will largely be defined differently by each hobbyist as they pursue their own interests. Collectors will define the age by the peak time of interest in their specific areas. The golden age for Standard Gauge and Postwar collecting has come and gone, but judging by my personal observations at York and other shows, we may be approaching the golden age for MPC collecting if not already at the beginning.
Personally, I am in my own golden age right now. I belong to an active club that spends 28-30 days a year (not counting setup time, which is fun, too)) running trains for the public (and always looking to do more), has weekly meetings and sometimes run sessions, goes on train-watching trips (sometimes long ones, like the two times we went chasing UP 4014), and do road trips to out of the area train shows and train shops. Add to that, I still have a lot of fun hunting for the items on my "unicorn list", finding stuff I never knew I wanted, talking trains with friends, reading about trains, and dreaming of the day when a personal layout becomes a possibility. So yes, my golden age is now, and is going to last pretty much as long as I can make it. 
Andy
