The BUILD trio (DN3D, Blood and SW) are all excellent games. I recommend anyone who has tried to at least try out Blood (IMO the best of the trio).
Other than that, if you are a FPS fan but haven't touched the 90s scene, please give yourself a favor by purchasing DOOM 1/DOOM 2/BUILD trio/QUAKE 1/QUAKE 2/UNREAL GOLD and more importantly download modern engine improvements, play the games and even more important, find communities and download the top quality mods/mappacks and play all of them.
Seriously I think it will take one years to go through the whole process, even limited to top quality mods/mappacks.