Using just goals and assists over an entire period isn't conclusive evidence, Nani played in a different formation and was never used as a striker like Martial and Rashford. Martial and Rashford have always played in a 4-3-3 or 4-2-3-1, whereas Nani was mainly used in a slightly deeper role in a 4-4-2. Having that second striker in there affects the player goal and assist % distribution across the team, in a 4-3-3 the goal/assist % is more concentrated across the front 3 positions, whereas it is more spread across 4 positions in a 4-4-2. As an example of this If you look at Rashford's numbers you can see his stats drop after Bruno takes up that support striker role (pre surgery and MBE), causing the formation to become more of a 4-2-5-1 than 4-3-3, this is because there are 4 forwards instead of 3. Having said all that, Nani was close to world class in 2011 with only Messi, Ronaldo, Robben and Ribery being superior at the time, Rashford and Martial have never touched those heights. Nani wins the eye test comfortably.@altodevil
As I said...debateable.
He was a good player. He had a few outstanding seasons. He never once had to shoulder the attacking responsiblity of the team.
Call me out yourself mate. The stats are available to debate.