the motivation of the Reapers makes them like a retarded version of the Anti-Spirals. Anti-Spirals sought to eliminate and/or oppress spiral lifeforms so they don't grow to the point of invoking the spiral nemesis and imploding the universe. The Reapers keep wiping out organic races and turning at least some of them into Reapers... to prevent them from creating an advanced synthetic race that would eliminate all organic life period. It'd make more sense if it WERE closer to the Anti-Spirals, that they keep wiping out advanced races so as to keep them from completely dominating the galaxy, draining resources, and prohibiting other races from ever rising. You actually see some examples where they could already be cemented as a valid reason, the Krogan reproduce/mature quickly, live extraordinarily long lives, and are absurdly resilient so they seriously could've dominated the galaxy had it not been for the genophage, and you also had the Protheans who we discover subjected and enslaved other races all the time, allowing no one else to reach their heights unless they successfully rebelled and overthrew them.