I was really struck by this rare cover image for the latest Comics Revue by Tom Yeates which pairs The Phantom and Tarzan of the Apes. It's appropriate since both have comic strips featured inside the volume, but it does shout out that we need a meeting of these two jungle heroes. Given the long life of Lord Greystoke and the generational nature of The Ghost Who Walks, it's an easy thing to arrange with several eras to choose from. I'd go with the heyday of adventure, the 30's myself, but I'd settle for a modern meeting.
Here's an earlier issue by Flash Gordon artist Jim Keefe featuring the duo, this time facing off against one another.
Previously the two had only joined up as part of a larger assembly of classic characters for centennial celebrations.
These are a couple of sweet images by the great George Perez.
On a final note, I did chance upon a story which did showcase these two jungle heroes (sort of) but it is decidedly NSFW. For a look at a story in which the "Fantum" encounters another jungle king called "Norman" check out this link. It features very lusty art by Alex Horley and a story not for the faint of heart.