Dr. Light's Role in the Megaman Series
Dr. Light is the "father" of Megaman, Roll and Protoman. So he was once Dr. Wily's best friend and colleague but the two became sworn enemies. Dr. Light sought to use his robots to help mankind while Dr. Wily sought to conquer the world to build a new era of scientific genius. Dr. Light's role wasn't all that expanded until Megaman 3 and he had some focus in Megaman 5. He would have a posthumous version of himself in the Megaman X series.
In Megaman 3, Dr. Wily pretended to change his ways which was a sham. Dr. Wily and Dr. Light built the eight robot masters in Megaman 3 to mine for elements for Gamma. Dr. Wily later stole Gamma which Megaman had to stop him. In Megaman 5 and 9, Dr. Wily kidnapped him. In Megaman 5, Dr. Wily sent a Protoman imposter later revealed to be his Darkman robot. In Megaman 9, Dr. Wily frames Dr. Light.
Dr. Light is responsible for many upgrades Megaman underwent throughout the series. In the original Megaman series, he was responsible for giving Megaman the mechanical dog Rush and later the chargeable Mega Buster to combat Dr. Wily's more advanced robots. He also created the Megaman/Rush upgrades for Megaman 6 and 7 which unfortunately, Dr. Wily implemented them into his rebellious robot Bass who is Megaman's anti-thesis.
In Megaman X series, Dr. Light exists as a holographic version of himself or what could be an A.I. version since Dr. Light died of old age. Dr. Light's role here was that he created Megaman X (though X could be Megaman upgraded and totally rebooted but Project Zero is just a fan game). Probably Dr. Light created an AI version of himself to continue his work to support Megaman X.