For stock triggers ...
Semi Auto: A tie between my father's Hi Standard Citation and his Kahr K9. Completely different personalities, but both are ultra slick with crisp breaks and not much overtravel.
Revolver: Pythons do have very smooth DA triggers, but to my finger, they have more stacking than Rugers.
Therefore, I gotta vote for Long-Action S&Ws. They are as velvety smooth as the Pythons right out of the box, but without stacking and an even better SA trigger, IMO. Gonna have to buy a LA M&P one of these days.
Of the guns I own, well, I only have one semi: a Springfield 1911 Mil-Spec. It has had a trigger job, which greatly improved it over stock form. Still, it isn't up to par with my dad's aforementioned Hi Standard and Kahr.
Of my revolvers, hmmm, tough call. But I'd say be a very slim margin, my 4" S&W Model 15 takes top honors. But a bunch of others aren't far behind (I'd say my 2" 15, 13, 14 and 17 all tie for 2nd). Even my J frame 642 is surprisingly smooth.