It's not the design aesthetic of the G1s that makes them seem more collectible... it's the materials they are made out of.
With G4, bodies and heads are different plastics that deteriorate quickly, eyes are slapped on decal-style, symbols are only on one side, hair is much sparser... so on and so forth.
While G1s have held up pretty well over 30 years, I keep hearing about G3s and G4s that have consistent deterioration issues. I don't think most G4s will be in great condition in 30 years, that's all.
Oh, as for the plastic thing, then we totally agree. That was my first remark.
![Smile :)](https://mlparena.com/Smileys/default/smile_001.gif)
I do think that some of it will break down, and mismatch. But some of that was seen in G1 times (yes only a few ponies).
I don't think the eyes, symbols, and sparse hair make them less collectible. I consider that part of the aesthetics.
But I do think there will be some that make it, I don't think 100% of them will be rubbish. So the ones that make it, will be collectible.