Alal-ud-din Khilji was the most famous Khilji ruler because of his military conquests and administrative reforms. He expanded the Delhi Sultanate's territory through successful campaigns against various kingdoms, including Gujarat, Rajasthan, and Madurai. He also introduced various administrative measures like market regulations, land reforms, and a centralized taxation system. Additionally, his reign is known for its cultural patronage, particularly in the field of architecture. Alal-ud-din Khilji's military successes, administrative reforms, and cultural contributions made him the most famous ruler of the Khilji dynasty.