Ironically, these are still the best games for a LAN party. I set up a fleet of old cheap computers running Linux, loaded with all these offline and now open-source games. We had a blast and ended up playing mostly Quake 3 until about 4-5am.

We couldn't play any modern games, because every single person at the party would have had to have a Steam account or some license to the game, and have to log into it on my computers, then sign out when they were done... what a bunch of garbage. Nobody had their Steam passwords on hand.

With Quake3, you could sit down on any free machine and jump into a game instantly. I was also really surprised because some computers had the "official" Quake 3 purchased from Steam on Windows (friends who brought their own computers), some had the open source Quake 3 engine running on Linux, and some had official Linux clients... and they all worked together flawlessly.

Red Alert was a favorite. Unreal Tournament: GOTYE was another. Also AOE2. I still play AOE2 with friends occasionally.