If we take the scale of regional dominance and effect on society in to account,certainly the British empire had played an enormous role in the history of the subcontinent. With their cunning expansionism policy and the introduction of western science,technology,literature and the idea of Renaissance the region underwent through an transformation during the late 17th Century.
But as an Indian,no matter how it has ill shaped itself today, the idea of democracy should be considered as a blessing and pride to us and most notably,none of the Monarchy could be attributed for this modern idea of a republic much before even Plato had envisaged of. The sixteen republics of Northern India namely Anga,Magadha,Kashi,Kaushala,Bajji,Malla,Cheti,Bansha,Kuru,Panchala,Matsa,Sursena,Asmaka,Avanti,Gandhara and Kamboja were the most prosperous republics remarkably shined in their contemporary ages. The power of Parishad during the Buddhist period was so extraordinary that it once rejected Asoka's verdict because it was not given in a written form. The idea of a system of court much resembling the Areopagus of Athene or Spartan Gerousia was the brotherly form of Mahallaka.
So for me,the biggest effective system which we Indians are enjoying today did came from a group of republics whose antiquity goes almost three thousand years back,and certainly not from any Monarchical/Empirical regime.