For those who are interested, you need certain decisions from ME2 to save both races, it's not just blind choices;
"Geth vs. Quarians
In order to achieve peace between the two races, you need to get 5 to 7 points. These points are based on your ME2 and ME3 decisions. If you have 4 points or below, you cannot achieve peace.
-Rewrote the Heretics (0 points)
-Destroyed the Heretics (+2 points)
-Tali is NOT exiled (+2 points)
-Tali has been exiled/You did not do the Loyalty Mission (0 points)
-Resolved Legion/Tali conflict either using the Paragon or Renegade options (+1 point)
-N7 Mission: Save the Admiral on Rannoch in ME3 (+1 point)
-N7 Mission: Destroy Geth Squadron on Rannoch in ME3 (+1 point)
-Completed Legion's Mission in ME3 (or no peace)
You will need a HIGH reputation for the peace talks. If you rewrote the heretics in ME2 BUT achieve peace, you will gain more war assets, but there'll be less quarians. Also, if you rewrote them, you will face more geth than people who destroyed them, in which they'll face less geth."
OT: Maybe it's because I didn't romance Tali but the Geth were much more worthy of living than the Quarians were to me. After about my second playthrough I realised that you can save both sides. But even so, to a lesser degree in ME2 but more so in ME3, the Quarians in general are well... dicks.
They distrust me helping Tali in ME2 with her trial thingy, they fire on a ship with me inside after I just did them a huge favour to save their collective fleet asses by stopping the Reaper signal, they are generally condescending towards me and I think it was their own damn fault that they lost their planet to the Geth in the first place. So they should either accept their fate as a space-born fleet forever and shut up about their homeworld. They make the Geth out as some kind of super evil race that hounded them from their own planet when they created them, then they tried to destroy them. If the Geth show self preservation, which they do, then they are truely living. Yet the Quarians still treated them as machines that have no emotion. Also, "Oh there's a full scale Reaper invasion of the Galaxy? Let's initiate a war with two rediculously large fleets to take back our home world that will probably be eaten by Reapers in a few weeks anyway"
Also Legion is a much better squad member than Tali and is a much more interesting character than those faceless[footnote]See what I did there?[/footnote] Quarians.
So yeah, the Geth live and the Quarians die. No regrets