Oh, the memories! Delta Force 2 over multiplayer, with, I think, 30 players or more, on 56K was surprisingly fun! Advanced voxel engines are quite impressive.
I played both (1 and 2) almost exclusively in single player, completing every mission. SP missions in DF2 were much, much harder by comparison. Unlike the helicopters in DF1, the MIL Mi-24 Hind helicopters in DF2 were able to shoot at you and you were only able to eliminate them either with an anti-tank missile or with the grenade launcher. No matter how many magazines you emptied at a vehicle, it stayed there and didn't explode :-(