I've thought about this a bit and believe that if the artifacts were not taken out of the country in some clanedestine manner, then they belong to the finders.
Just because nowadays they look back with regret at the lost tourism opportunities, does not mean all the artifacts others funded the search for should be returned.
I would possibly make an exception for mummies. Those are people with possible descendants alive now, and I could understand not wanting my great great granddad on display in a museum, or even my collateral great great grand uncle. I'd expect compensation for the expedition costs, though.
<Why is it that somehow we give so much credibility to governments, when the same claims would be laughed out of court if advanced by individuals. Many of these governments didn't exist in their present form when the various articles were taken, and so what does "ownership" even mean? Is the world better served by these kinds of things being examined in a center of scholarly research or squirrled away in some corner of a piss ant country somewhere?