Here’s my results.

rank options 1 Mob of the Dead 2 Call of the Dead 3 Moon 4 Ancient Evil 5 Moon (ZC) 6 Origins (ZC) 7 Kino Der Toten (ZC) 8 Zombie Verrückt (ZC) 9 Origins 10 Der Eisendrache 11 Buried 12 Der Riese 13 Kino Der Toten 14 Mauer Der Toten 15 Revelations 16 Zombies in Spaceland 17 Shangri-La (ZC) 18 Gorod Krovi 19 Shangri-La 20 Shadows of Evil 21 Nacht der Untoten (ZC) 22 Five 23 The Giant 24 Zombie Verrückt 25 Nacht der Unoten 26 Die Rise 27 Outbreak (Exo-Zombies) 28 Shi No Numa (ZC) 29 Ascension (ZC) 30 Die Maschine 31 IX 32 Firebase Z 33 Outbreak (Cold War) 34 Dead of the Night 35 Classified 36 Alpha Omega 37 Tag Der Toten 38 Voyage of Despair 39 Dead Ops Arcade 3 40 Blood of the Dead 41 Dead Ops Arcade 2: Cyber’s Avenging 41 Zetsubou No Shima 43 Ascension 44 Shi No Numa 45 Town 46 Nuketown Zombies 47 Dead Ops Arcade 1 48 TranZit 49 Farm 50 Bus Depot 51 Burgertown 51 Carrier 51 Descent 51 Rave in the Redwoods 51 Shaolin Shuffle 51 Attack of the Radioactive Thing 51 The Beast from Beyond 51 The Final Reich 51 Gröesten Haus 51 The Darkest Shore 51 The Shadowed Throne 51 The Tortured Path 51 The Frozen Dawn