I think pacing is of it’s time. Movies that seemed perfectly paced on release can seem slow now, as pacing has changed. So, to me, there is no such thing as perfect pacing as the movie may seem different in retrospect, which doesn’t take away from it.

Look at purposeful slowing of the pace in anime scenes. Look at intentionally hyper fast pacing in thrillers like Taken. Both have more artistic merit than a well paced marvel movie that moves along but feels pedestrian.

Playing with pacing can also make it fun, like memento or pulp fiction.

I’d say, particularly well paced films are usually long epics like gladiator, braveheart, titanic, lord of the rings: as they need to be to carry the audience through a longer narrative. Or twisty thrillers that change course and weave, so you don’t stop to think too much and miss the magic, like sixth sense or silence of the lambs.

Interesting question, though.