For ultra purity, there's basically only Chocolate Doom (or DOSbox and the original game). For modern features (but losing the Doom "feel"), (G)Zdoom or Doomsda

For ultra purity, there's basically only Chocolate Doom (or DOSbox and the original game). For modern features (but losing the Doom "feel"), (G)Zdoom or Doomsday; for stuff in the middle, Doomretro, Crispy Doom, Prboom+, Eternity. I'd say Crispy Doom (or Doomretro on Windows) are good balances.