We watched this back-to-back with the 1940 version, and the main thing that struck us was how little the effects had improved - two decades may have passed, but this was obviously made on a much smaller budget. There's no young sidekick or genie here either; it's just Karim (Reeves), who sees the beautiful Amina (Moll) and has to pass through a series of trials, in order to find a blue rose, the only thing that will stop her from wasting away. Both Reeves and Moll are great; unlike Duprez in the earlier version, Moll isn't a wallflower with no personality. Chamarat also stands out, as a spectral figure who assists the hero when the need arises.
The film's major shortcoming is perhaps the lack of a real villain; there's a rival for Amina's affections (Dominici), but he isn't what you'd call particularly evil. It's mostly hero vs. trials, some of which are pretty cool, not least the battle against a horde of (literally) faceless minions. There's also the evil sorceress with a nice line in statuary, an invisible guy guarding a bridge, that kind of stuff - the feel here is close to The Odyssey. You do get a battle at the end between Karim's army and that of the rival, though the outcome won't surprise anyone; however, the finale, with the blue rose, is genuinely affecting. There was another version made for TV in 1978, with the thief again a sidekick (Roddy McDowell), but it's rarely mentioned - likely for good reason.