>>714455939SS1 is the most complexity you can get out of the retro Doom styled shooters, there's like 20 weapons with multiple ammo types.
SS2 is kind of comparable to DX I guess but actually good. Multiple ammo types, skills required to use them, upgrades, different firing modes. You point the crosshair at something and it shoots there, simple.
Both hold up well gameplay wise but the SS1 level design will kick your ass. The fact that it came out BEFORE Doom 2 is mind boggling with how modern it feels. Leaning, free aim, inventory management, exploration, it's fucking insane.