At the time, Heston was a relative unknown, who managed to get the part after DeMille saw him on the lot at the studio. But Heston holds the film together, despite his inexperience. There's much here that echoes his portrayal as Moses. in the first part of The Ten Commandments Moses is shown to be an expert master builder marshalling an army of people to pull off an incredible feat of erecting Egypt's ancient buildings and there's much of that here too. Such is the size of the circus here that its often been show that it's the circus that us the real star if the show.
Then there's Brad/Moses' drive, focussed on the end goal and not easily swayed from his vision of the right outcome by personal sacrifices of those close to him. Several time in The Greatest Show on Earth the comment is made that he instead of blood he has sawdust in his veins,and a similar trait appears after Moses' encounter with the burning bush, where he's so focussed on freeing the Israelites that he leaves his wife behind and pains Ramsees whom he clearly cares for a great deal.
There's also the love triangle in both films Heston is loved by two women, seems largely detached from deep feeling for either of them, but ultimately leaves one of them disappointed (although they both marry someone else). I can't quite put my finger on the exact similarity between Gloria Grahame and Anne Baxter, aside from them being stars of key films noir, but there's a certain girl-next door approachability about them both even though one is a Princess and the other rides elephants.
For DeMille's part there's no 10 minute prologue in The Greatest Show on Earth as there is in The Ten Commandments, but DeMille does do the voice overs, moving the story at several key points and revelling in the kind of pomposity that so defines his films in general.
The performances are pretty good, though Jimmy Stewart steals the show in a role that ultimately makes me wondered if it influenced the performance of another Moses actor, Burt Lancaster, 37 years later in Field of Dreams. Also, as influence on later films goes I cant help wondering if one of the more memorable lines from Donnie Darko owes a debt to one exchange featuring Stewart.
But it is the circus tricks that really sets this apart from its contemporaries, particularly as these days films want to be able to say "no animals were harmed in the making of this film". Circuses have a reputation for animal cruelty - though it's possible that many are cruelty free - but it has to be conceded that many of the scenes of animals doing things were hugely impressive and, for anyone born after 1952, this is as guilt-free a way of seeing such spectacular achievements as I can think of.
So if you've not seen it, I would recommend it. It's not a Bible film as such but informs The Ten Commandments a little and it showcases DeMille and Heston at the top of their games.