These could be games that left a lasting impression on you, games that had stellar gameplay mechanics, characters that captivated you, games that you played tons of hours on, etc.
Battlefront & battlefront 2 first and foremost for sure. Classic battles for socializing, space battles for crash fun, single player galactic conquest
Battle for Middle Earth 2. Big improvement over 1 and you could play as anyone, although Men was outrageously overpowered
Unreal Tournament 1999
Starcraft: Broodwar. We were shitty turtle players, but so much fun
Warcraft 3 (mostly dota, twilight's eve, and TD)
CS 1.6 and CS:S
Mario kart double dash
super smash Bros melee
Fire Emblem: Sacred Stones
Pokemon Emerald
They don't make games like that anymore, but then again, it is definitely 75% nostalgia and the good times with friends that I had during those years instead of the actual games.
Now we are stuck playing CS2 online getting rolled by kids on shitty comp servers with 100+ ping 1 day per month or so because there is a 7 hour time difference now. Because online games without sweaty, toxic communities are pretty far in between. Miss the days when video games were fun lol