90s kid, and I grew up playing Counterstrike and the Warcraft/Starcraft series online. Multiplayer games tend to be the most fun when you've got a community of people around you to game with, and that's something high school / college provides in spades but adult life really finds lacking.

I'm mostly sad I was a bit too old to get into the Collaborative/Competitive game scene - that sweet mix of RTS and FPS you got from Tribes or the more heavily modded versions of Team Fortress or EVE Online, where you would build up a base's tech tree before launching a climactic battle against your opponent's main base.

Interacting with other humans and following the strategic "meta" to execute increasingly elaborate plays and strategies adds depth to relatively simple games. Whether I'm playing tennis or battling it out in the technodrome, there's something fun about the PvP experience that PvE can't replicate.