Grove Street takes down a small-time police department, the 3rd Street Saints take down the U.S. Military, and planetary alien threat, LOL, WONDER WHO WINS? Oh, and Johnny Gat single-handedly beats the entirety of Grove Street in a fight on his own, if the boss joins them, it is overkill.
I don't really see what impact San Andreas would have on the 3rd Street Saints. :/ The saints are a bit too high class to pay CJ and Grove Street any mind.
Well I'm pretty sure it's canon that Grove literally took over every gang territory in San Andreas, plus they've got an up and coming garage/chop shop, a stake in a casino, and CJ is the manager of one of the top rappers in the world. Plus they took down the biggest drug operation in the state and exposed some corrupt cops. The Saints as big as they are wouldn't ignore something like that. Boss would probably think CJ was a badass(especially if he's ripped) and offer him a spot or to buy his gang out or something. He respects fellow badasses who don't cross him and who are literal one man armies. I'd say given time he would come to respect CJ as much as he does Gat.
The Saints can stomp all of GTA. Put all the protagonists, all the gangs, with all weaponry, all the police, SWAT and army and canon resources together, the Saints can still stomp them.
Look at this, by the end of Saints Row 3, the Saints have taken over Stilwater and Steelport. The Grove Street Families can, canonically, only take over Los Santos, the rest of cities in the San Andreas states are out of limits. By doing this, the Saints have defeated gangs that literally had at their disposal things such as voodoo magic users and superhuman clones. And then they took on a Law Enforcement group (STAG) that seemed out of a ****ing sci fi movie, complete with laser weaponry, tanks that fire lasers, and hyper technological VTOLs. The Saints still took them down and seized their technological resources, as they did with all the other gangs. Compared to that, what has the SA cast done? Took down a bunch of corrupt police officers, and had runs at a run of the mille gang or mafia boss.
They have access to hyper-competent hackers, the means to mass produce superhuman clones (which their main echelons can take down), they have aircraft, VTOLs and ****ing tanks, ****ing zombie viruses, and a long list of etcs. They also have their little alliance with Ultor. By the beginning of Saints Row 4, the Boss is the ****ing President of the mother****ing USA. And his epithet comes with a literal paragraph that says that he has nukes available whenever he wants by only pushing a button.
And by the end of that game... the Boss is a mother****ing galactic emperor. The Saints literally have access to the resources of the whole Zin Empire. Which comes with spaceships, mecha and power armor that can give the people wearing them superpowers equal to those of the Steelport simulation.
Shit, Johnny Gat has taken over Hell. The Saints left the realm of "street gang" by the time Saints Row 3 ended. The whole GTA universe stands no ****ing chance.