In what order should a newcomer watch Star Wars episodes?

The Vulture website has aggregated the suggested viewing orders from a range of people involved in the original, prequel and new trilogies

George Lucas (I, II, III, IV, V, VI): “Start with one. That’s the way
to do it right: 1, 2, 3, 4, 5, 6. That’s the way they’re supposed to
be done. Just because it took a long time to film it doesn’t mean you
don’t do it in order.”

Daisy Ridley (I, II, III, IV, V, VI): "I would say 1, 2, 3, 4, 5, 6,
because for a young person it's easier to understand the chronology."

John Boyega (?): "I would say whatever you want! Watch 3, 6, 2, 1 — do
whatever you want to do so long as you experience it a very unique way
and enjoy it."

Mark Ruffalo (IV, V, VI, I, II, III): "From the first one made to the
most recent. Straight through. They just build up nicely that way.
That’s the way I saw it, and I’m a little bit of a throwback."

Aaron Paul (IV, V, VI, I, II, III): "You start with the original Star
Wars movie. There is no other way. Maybe it’s nostalgia. Or maybe it’s
not even that. I have no idea why I feel this way, but you should
watch them in the order they were released."

They also offered the advice of a professional movie critic

Matt Zoller Seitz, critic (IV, V, I, II, III, VI): "The Godfather,
Part II order. This is the order my wife came up with back in 2005. We
were discussing the right order in which to show the movies to our
kids, and we agreed that Darth Vader's reveal was such a big deal that
it would be a shame to ruin it by showing the episodes in numerical
order. She was a big fan of The Godfather, Part II, which flashes back
and forth between Michael Corleone in 1959 and his father Vito as a
young man in the late 19th and early 20th centuries."

"In this order, you start with A New Hope and continue through Empire,
which of course ends with Vader dropping that huge plot bomb on Luke.
Then you "flash back" to The Phantom Menace, Attack of the Clones, and
then Revenge of the Sith to show how Anakin became Darth Vader. Then
you finish with Return of the Jedi, where Luke tries to pull his
father back from the Dark Side and at least partially redeem him,
restoring balance to the Force in the process. We actually watched the
films this way, and it really worked.

"Not only did it magnify the impact of the throne-room scenes in Jedi,
it made it much easier to see the mirroring games that George Lucas
was playing in the prequels, making The Phantom Menace a rhyme of A
New Hope, The Empire Strikes Back with Attack of the Clones (right
down to the sad cliff-hanger ending), and Jedi the answer to Sith,
following right on its armored heels."