As noted, Stalingrad cost Hitler the war. Ironically, at the height of the German advance into the Soviet Union, Axis armies were only about 12 miles from Moscow. Had Hitler pushed his advantage and taken the capitol, the Soviet Union might well have capitulated!
The fact that he did not, and placed his bets on Stalingrad shows his degree of megalomania -- Hitler chose to humiliate the leader of the Soviet Union by controlling his namesake city, rather than controlling the more strategic capitol city.
What's in a name? How history might have changed if Stalingrad had remained as Tsaritsyn!