well, I can add that ford v8's are very durable, it's very common to see them top 400K miles regularly on nyc taxi cabs, & I've seen some hit 500 & 600 & more on the original engine... chevys never make it that far....
I used to think the 86-87 buick grand national was a great engine, way ahead of it's time, not so much the engine itself but the whole package, I used to put GN engines in everything

ok, so there a little dated now...
the gm northstar was/is a great bit of engineering....
I wouldn't say any of the above deserves a title of "best" though, maybe notable....
gm's newest LS series engines are pretty great... I wouldn't mind having one of those
the best? hmmm, don't know if there really can be any answer to that, there are too many things that can be considered criteria, durability, efficiency, quite &smooth, making big power... the best engine in a commuter car has nothing to do with the best engine at the track, too many different things that one can be the best at, best all around would be a balance of all criteria, but then others will be better at certain aspects than even the best all around.
taking that into account, there is no such thing as the best
