Godzilla: If it's his post-mutation radioactive version then no you cannot eat him. If it's his premutation state without radioactivity, then maybe.
Ebirah: Yes, you can eat him. I will turn him into the world's largest shrimp tempura. I will eat him even if it kills me.
Rodan: In his post-mutation radioactive version then no. If it's his pre-mutation version without radioactivity maybe. But there's not much meat on him. Mainly his legs and abdomen. It's like eating a turkey but skinnier and larger.
Mothra: If it's the larva version yes though I would feel guilt. If it's the adult version yes but I would still feel guilt.
Anguirus: Yes if you remove the carapace.
King Ghidorah: I'm not sure due to his alien biology.
Gigan: No, he's a cyborg. He's more machine than monster at that point. This applies to both Showa era and Final Wars versions of Gigan.
Megalon: Yes, you can since he's a giant bug. Except for the drill bits.
Mecha Godzilla: No for almost all versions since he's a robot. Even Kiryu who has the bones of the original Godzilla, you couldn't eat because it's just the bones. I'm not sure there is even bone marrow left in them.
Kamacuras: Yes, he's a giant bug.
Oodako: Yes, the Toho crew literally ate him after filming his scenes in King Kong vs Godzilla.
Ganimes: Yes, he's literally a giant crab. It would be delicious.
King Kong: Yes though it would be weird to eat an ape.
Space Godzilla: I'm not sure how much of his body is crystals and how much is flesh. So, no.
Biollante: No, because she's part Godzilla and part plant. I'm not sure where the plant parts and the Godzilla parts begin and ends. Also, she spits out acid, the plant part of her is a rose which is not edible and the soul of a human girl is trapped in there.
Orga: No, he has millennian DNA and Godzilla DNA. I don't want to mutate if I eat him.
Megaguirus: Yes, you can. She's literally a giant bug
Varan: Yes, though I'm not sure how you would use the stretchy skin membrane. It's too stretchy to eat like it's chicken skin.
Gorosaurus: Yes, you can.
King Caesar: Technically he's a golem despite his mammalian appearance. He's made out of stone so no.
Minilla: Yes, but I would feel guilty over it.
Destroyah: Yes, he is a crustacean after all despite his demonic appearance. Though the oxygen destroyer might fuck you up.
Battra: Yes, you can since she's a giant bug for both larva and moth versions. I wouldn't feel guilt due to her anti-human views so fuck her.
Gamera: Yes, you can. Gamera is really neat and Gamera is full of meat. We all love Gamera!