Wave 1
The Reaper Fleet vs. 21st Century Humanity as we know it. The world has a 50 year warning (beginning in 2012) of the coming Reaper invasion in order to prepare. The warning is sent in a way that world leaders are entirely convinced that this invasion will occur, and they begin making the necessary arrangements immediately.
-Reapers Obviously
Wave 2
The Reaper Fleet vs. The UNSC of Halo Lore. The UNSC was nearly crushed by the Covenant...can they withstand the Reapers? They get no warning; the invasion occurs right as the UNSC is at the height of its power.
-This one could go either way, will not say anything on it.
Wave 3
The Reaper Fleet vs. The Covenant of Halo Lore. The Covenant are defeated by the UNSC due to internal conflict, but by themselves their technology is impressive. They are attacked at the height of their power, before discovering any humans.
Covenant Victory: DEW's on their ships and the fact that insanly high powered MACs needed several shots to take even the smallest Covenant ship down... doesn't bode well for the Reapers.
Wave 4
The Reaper Fleet vs. The full force of the Prothean Empire. Assume the cycle before the Protheans was able to shut down the Keeper signal and they have the same oppurtunity to fight back as Shep's cycle does. Will their advanced technology allow them to succeed in conventional warfare against the Reapers?
-Reaper Victory
Wave 5
The Reaper Fleet vs. The Star Wars galaxy. The Reapers come across the SW galaxy and see it as a place where organic life has run rampant; and see it as fit for their cycle of destruction. Can they contend with such an advanced organic society?
- Starwars Victory. DEW's can bypass Kinetic Barriers and as seen in ME1 they clearly do not have very much armor underneath the Kinetic barrier. Even if that doesn't mean anything considering the insanity of SW's weapons.
Wave 6
The Reaper Fleet vs. The combined fleets of Shepard's cycle and the Prothean cycle. Can this group finally beat the Reapers conventionally?
I say Shep and Protheans fleets. Personal Bias and because of ingame evidence provided.
For the final two waves. Pfft. Clearly War hammer and Star Trek both defeat the Reapers. Again Startrek utilizes weapons that, from what I know, use intense heat. Such is able to effectivly bypass Kinetic barriers..
And Warhammer is just ... insane.. I've never played the series and I know for a fact that SW's would be decimated. Does not leave much hope for our favorite machine Faction the Reapers..
Forerunners: (Not enough Data Available however we do know about their poor containment protocols when it comes to the Flood.)