In the last year or so of 8th edition, Marines were very strong, particularly when using the Iron Hands and Raven Guard Chapter rules.
There are very few 40k players who have never painted a Space Marine, and they remain the best-selling and most popular faction by a long way. The very origins of the setting lie with the Space Marines, beginning with the C100 release which existed prior to Rogue Trader, and then the iconic RTB01 Imperial Space Marines box which did so much to define the early look of 40k. Space Marines are the iconic faction of Warhammer 40,000.