Eipok Kruden said:
The Humans in the Halo universe never defeated the Flood. They merely prolonged the inevitable. The Flood is still out there. All they managed to do was defeat the Gravemind, which, as I've said earlier, isn't that big of a deal. The Gravemind can be replaced by another one.
As for the Asgard, it was my understanding that they have the Wraith to deal with. Even if they didn't, they still wouldn't be able to wipe out the Flood. The Asgard have never dealt with something like the Flood. The Flood is very different from the replicators. The Tollan are not exactly the best tacticians, as such, they would be wiped out swiftly. And I'm sure the Goa'uld hosts can be infected by the Flood and I highly doubt that a Goa'uld -- if a Goa'uld were to leave its host before its host was infected -- would be able to take control of a Flood form. Also, since there are so many Jaffa, many of whom live in fairly primitive cities and towns, they would be perfect for giving the Flood more "manpower," so to speak. The Stargate universe would be vulnerable. The only species capable of fighting the Flood would be the Replicators, which is why they are in this poll.
The Asgard are dead, extinct, so it wouldn't be their problem at all, the humans however now possess all of their knowledge, and have had it for awhile now.
The Jaffa are in the hands of Teal'c who was trained in the same style of combat as the humans (well not so much trained as he picked up on their style during the 10 years he has been hanging out with them) this would lead to one or two Jaffa worlds being infected but not much else as they would quickly rally to fight it, as they don't make use of AI's they won't have their effective fighting power reduced by a gravemind convincing their AI to betray them (as happened with the Ancients and the Forerunners),
The humans after a few fights with the flood they would know how to fight them and alter their strategy and structures accordingly, razor wire in air ducts preventing any movement, force-wide use of gas masks and shotguns, this ability to adapt on the drop of a dime is why the Stargate crew have a record of success which looks like this http://stargate.wikia.com/wiki/Tau%27ri#Major_Enemies .