Again you forget Bi han killed scorpion in both timelines. He's not as good he was just a place holder. Most people just see Sub zero not the person behind the mask. So in that Bi was the first and there for the most well Known.
Nope, just because he was the first doesn't mean he's the most well known. That's just got logical fallacy written all over it.
Here is my thing with Bi-Han. I feel like it was good story writing to turn him into Noob. He murdered Scorpion in life and he was evil. Even in the almighty mythologies Raiden tells him he is straight evil. If he does not change his ways Raiden fears for him. That's in mythologies. Quan (or shinnok can't remember which) makes a remark that Bi-Han will serve him one day as well. Bi-Han brushes this off like the pompous creature he is.
So what happens? Bi-Han does die. Bi-Han does go to the netherealm and Bi-Han does end up serving both Quan and Shinnok. It's good writing. The dude was a dick. He also had a chance to change per Raiden's instructions yet he didn't. He was just pompus and arrogant, and he paid for it.
So Kuai Liang comes along and could be exactly like his brother. Why does he have any reason not to be? However, he chooses to not be a dick. Instead he fights for good. Now I understand you don't like that because it somehow makes him boring to you, but in a way it's showing that sometimes the bad people do get what they deserve in the end
Noob then goes on to lead a dark organization (brotherhood of shadow). While Kuai Liang goes on to lead his own organization working for the forces of light (the lin kuei).
These two are some of the best written characters in the series.
One minor change of turning Bi-Han into Sub-Zero makes all of that story go to hell. Therefore it should not happen.
Also, two games both MKvsDC and MK9 were perfect opportunities to reintroduce Bi-Han as Sub-Zero. In MKvsDC boon used the most popular characters from MK. If it's like you say, and Bi-Han is indeed the more well known Sub-Zero then why did they use Kuai Liang?
In MK9 it would have went along with the whole d**n story to leave Bi-Han alive. The whole story was about making changes to the previous timeline. NRS could have chosen to leave Bi-Han as Sub-Zero and never have Scorpion kill him. That would have been a HUGE change
Did that happen though? I think you can answer that question. Bi-Han is merely Ben parker in the equation for Sub-Zero. He had to die for the true Sub-Zero to take his place.