One of the issues in military history is the lack of game theory that is applied to subject. There is a tendency to place undue bias on what determines "victory", whether by the battle or by the campaign. The most common of these is the zero sum game, or, either you won or you lost. To this we use hindsight to determine these parameters, either through total losses or who controlled the battlefield at is conclusion.
For example. Wilson's Creek is typically thought to be a Confederate victory, and surely in numbers loss and loss of control of the battlefield, they did. However, they failed to impose their will upon the Union. Union troops continued operations in the area, and indeed, the Confederates retreated across the Missouri Arkansas border. (Albeit not right away). So in this sense can Wilson's Creek be a victory?
Fort Donelson has a different outcome. By all intents, loss of the forts and territory, the casualties lost (Killed, Wounded, Missing, Captured) have a Confederate loss. Thusly Grant had accomplished his goals, and imposed his will upon the enemy. He would show much the same imposition during the Overland Campaign with his tenacious tactics and operational movement versus Lee. Whereas similar losses would have had the Army of the Potomac scurrying back across the river, Grant shifted, and continued to wage war.