Brady's the GOAT, hands down. But even as a Pats fan I have to say Mahomes.
Something to factor in is that those Patriots defenses in the early 2000s were really, really good too and helped big time.
But as Donoghus also said, it's true, Brady has had almost 3 HOF-level careers if you think about it. We'll see if Mahomes can have Parts 2 and 3. Brady was also iron man after the 2008 ACL injury, while Mahomes has already dealt with some big injuries. It remains to be seen if he can hold up through his 30s. Easier said than done. I remember when everyone was saying the likes of Russell Wilson, Aaron Rodgers, Cam Newton, etc. would start a new dynasty and easily win 3+ rings, but ultimately they all kind of fizzled out due to some choking/injuries.