I've no formal training in history, so I'm curious to see what criteria are used to determine how a military leader is viewed in the present.

Are things like strategic vs tactics vs logistics matter in terms of evaluating a leader? Are technological and numerical factors important as well in elevating or diminishing how much impact a person made on the success or failure of battles/campaigns?

For example, I consider Gaius Marius one of the best and more influential of Roman Generals due to his reforms of the Legions and events following his death and defeat of the Marians on the late Republican period. But what exactly classifies a "Great General"? Crassus never received this glory inspite of his successes in Sulla's campaign against the Marians, and it's pretty evident how that messed with his head.