What are some retro games that you never played as a kid, but picked up for the first time when you were older than 30, and really enjoyed them?

Basically looking for any retro games that have aged really well, and can be enjoyed without having to have nostalgia for them on any console or PC.

Edit: Wow, so many awesome suggestions. Thanks a lot. It will take some time to try all of these but I'm going to go through these one at a time and will give them a good try.