Now it's my turn to sigh.
A good/great quality game =/= a game that sells system. I am sure there are many heart-broken Bayonetta 2 fans in GAF that can tell you that.
In terms of Sony, the only franchise that I can think of that I think qualify for a system seller moniker would be perhaps Gran Turismo.
I agree however, to your assertion that it is a combination of A B C D E F G that sells PS4 so far. I just don't personally think Sony has a single A or B or C that is strong enough to be called a system seller, at least so far. Well, perhaps I am wrong.
Your definition of a 'system seller' is subjective, vague and pointless. When a consoles sells well because it has an A B C D E F G shitload of great games, there's no point in complaining 'yes, but it doesn't have 'just' A and B'.
Having 7 games worth buying a console for is better than just having 1 or 2 games. In no way does this mean game A and B are worth more than C D E F G. It simply means game A or B are worth more
for the platform to sell well.
In a sense, a console having 1 or 2 system sellers is not a good sign.
When you look at the history of gaming platform and games being glamoured as 'system sellers' it's because:
a. the platform was selling poorly and relied on just one or two franchises to keep it's sales up: Halo (xbox), RE4 (GC), Monster Hunter (PSP), MGS4 (PS3), Titanfall (XBone), Mario xxx (Wii U)
b. the platform was an anomaly called the Wii where people bought 30 million copies of Wii fit/sport/play each
Well, like I said, Nintendo has survived so far so long mainly due to the strength of its 1st party offerings. If their 1st party offerings don't have the strength to sell or support their system, I doubt they would have made it this far.
You're using double standards here.
You can't state Nintendo's first party games are systemsellers for the Wii U and at the same time state that better selling games like FIFA, CoD, GTA aren't systemsellers for the PS4.