So I went through the two Devilman OVA's released by ADV back in the day (Devilman: The Birth and Devilman: Demon Bird). I liked them, although the former is definitely better than the latter. Demon Bird just feels like a protracted fight scene, which is fine in itself, but the setup was a bit weak. The villains don't get much development - I guess the creepy bird lady with wings on her head is in love with the cat-headed laser-shooting Blastoise, but that's about all I know. I also think the first 13 minutes could've been made into a stand-alone thing, since they don't have much (if any) connection to the rest of the film. Overall, though, it was still enjoyable.
The Birth was more interesting, though, since it deals with Devilman's origins and actually bothers to develop its characters - something which Demon Bird lacked (but didn't necessarily need, what with being the sequel and all). I don't have much to say about it except that it's worth a watch. And also a car door transforms into a tentacled vagina monster, but that's nothing shocking.
"Available for your home in 1995, only on Nintendo Ultra 64!"