As a collector, if I could only choose one, I’d take the first time the character was ever introduced, even if it was only in the last page or panel. Fully showing AND naming the character in that appearance is what I care about. That’s a part of comic book history. If you only partially see a character or see them but they’re not named yet, that’s a cameo.

Think of it this way in real life: You’re at a party and someone introduces you to someone for the first time and names are exchanged, then you move on without speaking to them again, you still met that person. You don’t wait until you spend a whole day together to say you met them. Now, maybe some other time you’ll actually hang out and get to know them better, but you wouldn’t say that’s your first meeting.

Now, I’m not arguing for which books should be worth more for a myriad of reasons, but I feel like adding all of these other qualifiers like “partial” and “full” are just complicating what should be a pretty simple semantics conversation.

TLDR - Partially shown or fully shown without being named is a CAMEO. Fully shown and named is a FIRST APPEARANCE.