“Sir”. I don’t really see any reason to call him anything else - I’m not a diplomat and he’s no better and probably no worse than anyone else I might meet on the street.
In what context are we meeting him in? If he happened to just be around I’d probably be indifferent. If he insisted I talk with him, I think I’d refer to him by his first name.
How about Raël? The title he uses is in fact “His Holiness”, even if it isn’t mentioned in this article. I’d probably call the Pope and the Dalai Lama “Your Holiness”, but not Raël, I think. Why not? I guess it’s because the Pope and the Dalai Lama are recognized as the heads of important and old religious organizations, while Raël is basically the leader of a cult.
Hyoo-MAHN. But only if I got to practice my Grand Nagus imitation for half an hour first.
I’d address him as “Your Holiness” upon introduction, and “Sir” afterward. That’s standard for royalty. Oddly will I don’t have a problem addressing nuns as “Sister” or monks as “Brother” I can never bring myself to address a priest as father. I’m an atheist.
Because ‘some random person’ is a nobody who’s done nothing to deserve an honour and isn’t called ‘holiness’ or ‘emperor’ by tradition and the Pope is a somebody who has been given a job that comes with a very old title. Just curious - what would you call the CEO of your company, a Senator, and your president?
I’d call him “Your Holiness.” First because I wouldn’t want to make a scene. Second because it doesn’t mean anything to me. I’d call him “Your Cromulence” and it would mean the same.
Like others have said, it really depends on the circumstances in which we meet. If I was visiting a Catholic church or Vatican City, and was introduced to the Pope, I would probably call him “Your Holiness”. When in Rome, and all that (nyuk nyuk). If he showed up in my town and I bumped into him on the street, it’d be “Sir” just like any other guy I wasn’t acquainted with. Same goes for the President. If I was to meet him as the commander in cheif, it would be Mr. President. If he was wandering around in my yard, it’d be “Hey you!”
Atheist here.
Let’s just say that pronunciation and attitude are everything. 
“Sir”
Then I’d launch into my argument on Contraceptives, which I won’t go into here.
Sir, Sir and Sir. Same as the Pope.
Right off the bat, this disqualifies me. There are many people in the world who have earned my respect, over the years. This particular pope is not one of them.
Atheist here. I’d address him as “Your Holiness.” I like to adhere to proper etiquette when I can. And in this case, I wouldn’t feel like I’m violating my principles, since the concept of “holiness” means virtually nothing to me.
Even a fairly random person such as myself can hold an ancient title, but more to the point - the Popemeister is just another politician IMHO, and thus receives the same [DEL]lack of[/DEL] respect as Dubya.
Gotta remember that I am in “a state of grave sin” in his eyes, and 300+ years of friction between my order and his suggest he wouldn’t respect me any more than I do him.
Sir/Ma’am, Sir/Ma’am, Dubya
I would probably refer to him as “The freakin’ pope!” and be promptly tackled by security.
Interesting question. I’m a deist, married to a Catholic, so I would definitely get the elbow in the ribs if I didn’t address the Pope correctly. “Your holiness” wouldn’t bother me, though. I’ve addressed priests as “Father” and nuns as “Sister.” Just a sign of respect, once my husband taught me the proper Catholic forms of address.
I met the Dalai Lama a couple of times, but I never addressed him as anything. Just, “Hello, nice to meet you,” sort of stuff. Now I see I must have made some horrible religious faux pas, but he didn’t seem to mind. Nice guy, there.
Hey Pope! What’s going on?
j/k
I’d be scared of saying the wrong thing. I’d probably say hello and wait for him to make a move.
“Your Holiness” and I’d address GWB as “Mr President”.
How did the Pope address GWB? 
“Your Holiness” is the proper honorific. I would no more omit that than I would “Mr. President” in front of Bush, or “Champ” while speaking to Joe Frazier.
“Hey pope baby, whaddya really think about this Da Vinci Code stuff?”