Do you think that a general's win- loss record on the battlefield is the best gauge of measuring greatness as a military leader? why or why not?

A general's win-loss record is only one thing to ponder upon. There are other factors. One is the competency of the opposition. So a lackluster general may fight an even worse general and end up looking good by winning. Weather may be a factor. A good general with a good plan may still lose because of bad weather. Good generals with good plans may be defeated may be defeated by an army with better weapons. There's also reputation to consider. Grant fought and won more than he lost. Other generals still complained to Lincoln about him saying he drank. Lincoln stayed with him saying he was needed because he fought. Lee may have been a better general than Grant but he did not have as many men and his men were poorly fed and supplies were inadequate.