What did the lliad and the Mahabharata have in common?

Both portray gods. Both contain stories of battles. In both cases, the historical truth of the war is in doubt and remains subject to scholarly discussions. Both are epic poems of considerable length. Both books describe only a limited period in a war that in both cases spans a considerably longer period. Both narratives describe individual battles and deaths of various heroes of both sides, military formations, war diplomacy, meetings and discussions among the characters, and the weapons used. Both are very old poems, their exact origins lost in the mist of times.