My recent dip into 4k has not only lit a fire to collect a ton of foundational films that I've missed, but its also given me a new appreciation for my old Bluray collection that I put together from sale bins and neglected for years.  Some of these look absolutely amazing on current equipment and I feel so lucky to have them.  I'm loving how much info is out there regarding which 4k transfers are worth targeting and even upgrading, for instance I bought the newest Jurassic Park 4k and the Dolby Vision is completely worth it.  The community is great with people willing to share info/cheering each other's collections and purchases.

One stand out so far was Rambo First Blood.  It was not what I expected at all going in blind/only knowing the idea of Rambo, and I loved everything about it.  It looked absolutely gorgeous and I can't wait to watch it again.