DDG, world-class talent but not a world-class player. Had periods where he just looked unbeatable in a somewhat woeful team. Unreal away against Real Madrid and Sevilla. However, we never got a chance to see him consistently at the highest level in Europe. He really missed his chance to cement his legacy when a dodgy fax machine prevented his move to Real.
The only time we saw him in high profile matches were for Spain and he didn't really fill the shoes of Casillas. World Cup 2018 completely destroyed his confidence and he's been declining ever since. So overall in my opinion he never fully fulfilled his potential to be the best keeper of a generation.
I still will have fond memories of DDG regardless. I think many United fans will appreciate his journey from a troubled start in 2012, to his peak years 2014-2018. Definitely was the only bright spot during a difficult period for the club, so he can still be regarded as a club legend, even if he's still behind the likes of Schmeichel and Van de Sar.