Zombies was more of a creative style of gameplay. I loved that about it. It took you away from the typical war-type gameplay that you see every time you play multiplayer and it kind of made you feel like you were playing a brand new game. They added a ray gun, a flamethrower, the wind thing, and the electric thing, and a waffle. They actually had some variety on it, and it actually required teamwork and was fun to play online with others. Spec-ops, well, I'd rather play multiplayer imo bcuz it's the same playstyle except instead of playing against AI, you play against real people. Spec ops was fun for the first day, then it got rather dull and repetitive. Like someone above mentioned, the mystery box makes a BIG difference. The element of luck, and hope, when you press that mystery box. You don't find that on spec-ops, it's like "Ok, I'm level 80 now, I want 'this gun' , 'this air support' , 'these perks'" let's go.
Spec Ops will never be the same as zombies... It will never be able to compare imo. UNLESS of course, they put a story mode behind it like zombies was, and it's based on whatever map is first, and the cutscene starts with a MOAB being called in. All of the soldiers on the good side die, except of course you and whoever you're playing with. Every soldier on the good team then turns into GIANT TEDDY BEARS WITH GOLDEN AKIMBO DESERT EAGLES, and they let you get classic weapons from all of the CoD's plus some new additions in a Mystery Box, and maybe instead of money to open it, (since it would be easy to spam at the beginning) make it so that you need a number of kills, like 50 or something, this forces you to use whatever gun for 50 kills and adds to the difficulty. I can keep going, I have ideas for days, but I think I'm done for now.