This is pretty simple to answer, IMO.
The Flood were SCARY when I first met them in Halo CE. Even by Halo 3 they were no joke.
The Prometheans were not scary. I think them being revealed before the game came out kind of ruined any surprise. Even then, the Prometheans lack personality. Not like the Flood have it either, but the Flood were truly scary.
Watchers are a pain in the arse, but easy to take out. Same with Crawlers. Knights, meh, they were never really a challenge.
When I compare beating the games on Legendary, Flood were tougher than Prometheans.
I hope in Halo 5 there are new enemies. Either new classes of Prometheans or finally some rogue still living Forerunners. I was disappointed that we never REALLY got to fight the Didact. Sure there is that QTE at the end of the Campaign, but it’s not the same as having to have a strategy to take him down. Just hit some buttons at the correct time and he’s toast.
I suspect the Flood are going to make a return to Halo, could be they are an instrument of the Precursors, could be that the Gravemind is a Precursor. Whichever… Prometheans really need to amp it up in Halo 5. We essentially had to beat birds, dogs, and quirky hunchback beetles.
The Flood were infected Humans, Elites, and Brutes. Definitely scarier as they were abominations. Prometheans are to armor and “clean.” Nothing really says, “Be scared of me!”
-Sal
Without a doubt, the Flood, as an enemy, have it hands down over Prometheans. The Prometheans were an interesting and tough opponent, but the Flood is just another matter altogether. From their introduction in Halo CE (the most intense scene in any game I have ever played), the Flood always turned everything on its head.
Having Flood in Halo 5 would be interesting, but I think we would have to be put in a Burn or have to face a Key Mind to really make it interesting.
The Prometheans were way more terrifying. The way they were so badly designed for gameplay still keeps me up at night. Scary stuff.
But seriously, the Flood were infinitely more interesting and scary than the Prometheans. I still remember the first time that I encountered them in the underground facility. Genuinely terrifying. The first time you encounter the knights is in a cutscene. The player already gets a good look at them before they even meet them in-game. All of the tension is lost.
The Flood on the other hand is built up for the first half of the level. You see shadows slipping between the trees, and blips on your radar in the fog. Questions start forming in the player’s mind as they progress. What’s that goo dripping from the ceiling? What’s with all the blood on the other side of that barricade? Why are there make-shift barricades to begin with? What do these symbols on the wall mean? What was this place used for? It’s a mystery you get to solve at your own pace as the player.
Flood. It’s a no brainer. It was a great idea to have something so small, carry so much power and spread like that. I remember my first play-through on CEA. for the first half it was: “Oh! Covenant, neat.” Then I hit the level 343 Guilty Spark. After that, it got real. Right off the bat you know something is wrong… very wrong. The crashed ships. The fleeing covenant. The abandon facility. The crazy marine. Then you reach THE room. Through the cut-scene it was “Huh? Something’s not quite right here… What was that? What’s going on? Eek! AHHH! WHAT THE !$%^@ IS THAT!!!!” Then it was an intense ‘run like hell’ part that I couldn’t sit still through. When I first saw promethans it was “Eh…” The only problem I ever had with the flood is ‘The Library’ *shudders* I mean, ugh…