I couldn't help but think about this poll when reading these threads:
www.enworld.org
www.enworld.org
It's interesting to note how our (collective) opinion matches up with the sales numbers. I personally voted for "old school" to be everything before WotC, because I see that as being the biggest epoch from both a business and game design perspective. But it seems like the more common definition is basically a map of what older edition has the most printed copies.
D&D General - TSR D&D sales numbers compiled by Benjamin Riggs
D&D historian Ben Riggs--author of the upcoming Slaying the Dragon, which is a history of TSR-era (not that TSR, the real one) D&D--compiled some sales figures of AD&D 1st Edition's Player's Handbook and Dungeon Master's Guide from 1979-1990. Behold! Some actual D&D sales numbers! While...

D&D General - Basic D&D Was Selling 600,000+/Year At One Point
Recently Ben Riggs shared some sales figures of AD&D 1st Edition. Now he has shared figures for Basic D&D from 1979-1995, and during the early 80s is was selling 500-700K copies per year. Ben Riggs' book, Slaying the Dragon, which is a history of TSR-era D&D, comes out soon, and you can...

It's interesting to note how our (collective) opinion matches up with the sales numbers. I personally voted for "old school" to be everything before WotC, because I see that as being the biggest epoch from both a business and game design perspective. But it seems like the more common definition is basically a map of what older edition has the most printed copies.