Cleopatra is a difficult work to talk about and with, because it's essentially a very long and occasionally meaningless sex pervert movie (or, to put it more professionally, an erotic arthouse film) that nonetheless has a lot of historical and artistic interest.
The story and characters both effectively exist only as vessels for the artistic intent that MushiPro wanted to convey, which careens between erotic, comedic, genuinely tragic, and completely abstract. It's a long, long movie with very poor pacing that can be difficult to sit through if you're not in the right mindset, especially since most of the plot is flat and it occasionally borders on being an unintelligible excuse for sex scenes that register more as outrageous or experimental rather than actually arousing in any measure.
The best parts of the movie are all in the technical aspects, from its bizarre and bewildering animation- it opens on a camera panning down a cardboard city and has an entire section with human actors that have painted on, animated heads- to its sound design. This movie effectively exists just for the people at MushiPro to do whatever they want with some vague outlines of premise attached to it. The parade of art styles and the Kabuki portrayal of Julius Caesar's death are probably my favorite sections of the film; it also pulls forward with bitingly satirical veiled political references at times, drawing parallels between Rome and the United States, Japan and Egypt.
Unfortunately even though it has a lot of artistic positives, the incredibly slow and tedious pacing along with the nonsense plot combine into a deadly sort of toxin that makes this film inimical to genuine enjoyment. It's very much a product of its era, and I don't think modern anime fans with mainstream sensibilities would get much out of it rather than disgust; even people who enjoy 'animator's anime', where the point is allowing the people at the studio to experiment and have fun rather than create a streamlined product, would probably have difficulty digesting this one- God knows I did.
Objectively, I would recommend this if you're a history nut on a 70s film binge and smoke a lot of weed, and have about three or four friends of that exact ken. It's also worth watching if you're researching MushiPro and Tezuka's career (in which case you've probably already encountered similar themes in his more mature manga). Otherwise, just go look up clips of the more interesting animated parts and you've saved yourself from two hours of drudgery.