First off I'd like to say, Horry is about as clutch as they get (aside of Jordan single handedly taking over games). When (especially) he was with the Lakers, PJ would keep him out most of the game then put him in (especially in playoffs and championship games) in the end to drain threes.
Now that I got off subject, I think of all the present day QBs (and I'm putting my homerism aside), Drew has the best chance of claiming G.O.A.T. IMHO, Montana has that label, and I know it's debatable, but Brees is more or less today's version of Montana. I think it's realistic to think Brees has another 2-4 championships in him as long as improvements on defense keep coming. The similarities between the two are almost eerie. If you look at both rosters (from the late 80s, early 90s) you can almost plug the names in at the same positions and it's pretty much a wash... Even on defense.