Here’s a real life VW classic story. As a kid, a neighbour of ours had a beetle. It was his pride and joy and he literally polished the paint off it, needing a full respray. Anyhow, he died almost 40 years ago and that car has sat in the garage ever since. His daughter gives it a spin every now and then but kept onto it thinking it would one day become valuable. What’s it worth now, £10k?!?
Basically a car needs to be rare, memorable or otherwise special to become valuable. Mk1 GTi ticks at least one box because it was the creator of the hot hatch genre and is now getting on a fair bit too, which limits the number of good examples. VR6s have that engine though I might personally prefer the Corrado version. Otherwise there’s quite a resurgence in values of 80s faves like R5 GT / 205 GTi but I don’t personally think Mk5’s will ever truly get there, not least of all with imminent decarbonisation getting in the way.
That said, I’ve been wrong before and sold my 964rs and e30 M3 long before they went to the moon price-wise...