In the single action world.....Freedom Arms / they're overbuilt to the point of absolutely rugged...and amazing pieces of craftmanship.
In the double action world ...its Colt and S&W...and its hard to pick one over the other in my view. There are pluses and minuses to each ...but either one will last for many generations. I think Ruger is a distant 3rd ...but still a solid gun....then there are the rest ( a very, very distant 4th ...or more...)..
in my opinion ....of course / and to some extent, longevity will depend on the round that is fired in the weapon ...and how the owner treats the gun. There are a few of my buddies I'd buy a used gun from in a heartbeat....and some that I would never buy a used gun from ( they aren't bad guys - but some of them take care of their guns ..and some of them abuse the daylights out of them)..