The phrase "system seller" refers to a video game that is so good or popular that it convinces people to buy a specific gaming console or system just to play that game. Full definition
It could well be a decent system seller for them too - judging by that game footage above, it looked pretty good back in 2009. (gamedynamo.com)
To further expand my post, I'm saying those games aren't system sellers. (thesixthaxis.com)
The Switch certainly won't be hurting for great games to play in 2018, though it feels like the console's next true system sellers are at least a year out. (tomsguide.com)