I'm a Patriots fan, and I think it's about a toss-up. But that was just an example. The best player at any team sport won't necessarily win championships. Marino was 100x better than Trent Dilfer.
That argument works for a lower number of championships, but the higher number you get, the more you gotta realize it's not a coincidence that these guys are winning 3,4,5,6 championships.
While not the only factor, stats aren't necessarily a great representation either. The 'better team' argument works both ways. I mean, if a guy is on a lesser team, he has to be the focal point and consequently gets better stats, especially in basketball. If a guy's on a better team, his production suffers a bit, as other players contribute. But, speaking generally, if he were on a worse team, perhaps he could put up much better stats.
I'm not sure where this puts Russell vs Chamberlain, but stats certainly isn't the only delineator.
Just for fun, RE Brady v Peyton, I look to playoff performance, when the stakes are the highest. Brady vastly outperforms Peyton. By a mile. Peyton was shoddy in inclement weather too. I don't even think Peyton's #2 overall. I'd take both Montana and Rodgers over him.