For me 07/08 he was having best individual season I've ever seen from any player since L.Ronaldo, and clearly by far best player in the world. I mean, I have never seen a winger could score that amount of goals before that, 40+ goals in a season from the wing, while he was also most skillful player in the world at that time too, it just totally defies my knowledge and concept of football at that time. You know, back in those time, best strikers in the world were expected to have 20-30+ goals, while you won’t expect best winger in the world to score more than 10-15 goals. He was most skillful winger in the world, and he scored 42. To me, it’s revolutionary moment of football.
08/09 he isn't quite as good as 07/08, as he clearly had his head half in Madrid, but still world class and comfortably the 2nd best player in the world on performance alone (Messi was best).
Then 09/10 he was back to his 07/08 form but was injured at Madrid for months.
From 10-13, he was performing at his best ever level with unreal output, for me he has overtaken peak L.Ronaldo at that period, in terms of overall performances+end products, as he has everything (pace, skills, tricks, goals, long shots, header, freekick, athleticism, drive etc), but unfortunately not only he was competing with peak Messi during that period, he was also competing together with peak Xavi+iniesta and best ever Barca. Imagine if that has happened in other period of football, more people would have rated his peak higher.
Its only from 14-15 onwards, he is more focus on stats and trophies rather than performances, become less involved in build up play, but he enjoyed more success during that period.