Sasuke was on a wall ready to cry for his life when Itachi was standing and ultimately died by his illness and overuse of chakraItachi died, just like he wanted. He never wanted to win that battle, and he couldn't have because of his sickness. He fought to his limit, and I think Sasuke won it in all fairness.
And despite the fact that he wanted to lose, according to Zetsu, Sasuke was on the verge of death and would probably have died if they didn't arrive
Tobi later said that he wouldn't be talking with Sasuke if Itachi truly tried to kill Sasuke
Itachi won the battle and got finished of by illness
Sasuke got rescued
Itachi's plan was successful
I think it's pretty clear that Itachi was the true victor