Well, back in the old C64 days I collected cracked games and until about 1998 I had a huge collection !
But then more and more collection-projects like e.g. Gamebase-64 were born and they got nearly everything I have because they worked worldwide over the internet. So, at this time I realised collecting cracked games is pretty useless as everyone can have that Gamebase-CDs in a few hours for something I have collected for several years !! Thats also a reason I didn't want to send some rare titles to Gamebase.
But, then I started to collect hardware as this is something you can really collect since it isn't copyable
And so I think like Akira has already said, collecting ADFs or other disk-images or ROM files is totally useless.
Only collecting hardware or original games makes sense.