What if Robert Baratheon had lived on and kept his realm peaceful until the arrival of Danerys and her army. Would Robert be able to repel the invading queen and her dragons, or would he fail for the first time in his life? I personally believe that if anyone could repel an invading army with dragons that it's Robert, since he's not only a military genius, but he's also the best warrior in Westeros. He could have probably won over Denerys' allies with his charismatic personality. Robert defeated the Targaryens once, so it's not out of reach to assume that he could do it a second time.