What I wish would come back is really good COOP PVE. I ran a hugely popular ut2004 Invasion server that we wrote a custom mutator for (Sudvasion). I had a T1 line to my house that just ran the servers. We had a solid dedicated group of people from all over the world playing that 24/7. Was the pinnacle of gaming for me. 18 years later I still chat with some of the community via steam disc etc.