The most popular N scale model trains can vary depending on factors such as region, time period, and personal preferences of model train enthusiasts. However, some of the most popular N scale model train manufacturers include Kato, Atlas, Bachmann, and Micro-Trains Line (MTL).

Within those manufacturers, some of the most popular N scale models include the Kato Unitrack system, Atlas Code 55 track, Bachmann E-Z Track system, and MTL's rolling stock and locomotives.

In terms of specific models, some of the most popular N scale locomotives include the Kato SD40-2, Atlas GP40, and Bachmann Spectrum GE Dash 8-40CW. For rolling stock, popular options include MTL's 50-foot boxcars, Kato's Gunderson MAXI-I well cars, and Atlas' ACF 50-foot boxcars.

It's worth noting that popularity can be subjective and can vary depending on individual preferences, so the most popular N scale model train for one person may differ from another.