[SifJar]

vs. MS/Nintendo/Sony - none of those companies will know if a customer has exclusively their consoles, or has other consoles & will buy games on other platforms; could be useful information.

vs. Valve/Epic - similar, AFAIK these are PC-only stores, so again wouldn't be able to determine if customers also have a console (or several) that they play games on.

vs. general retailers e.g. Amazon - more specialised to people buying games; with nothing to back this up, I'd guess that people buying games on e.g. Amazon are more likely to be buying as a gift vs people buying in a dedicated game store (and particularly being registered in a loyalty programme at a game store). (Not saying that most people buying games on Amazon are giving them as gifts, just probably a higher proportion than in gamestop). In cases like that, it's probably less beneficial to target an ad for a game at that person, as they were probably just buying what they were asked for etc.