I'd say his body of work in the Premier League during that peak 2014-2018 period is the best the league has seen, particularly in his sustained consistency of match-winning performances. But while others aged gracefully, his sharp drop-off and his failure to translate that level beyond the domestic game to international tournaments affects his legacy both within England and particularly elsewhere. International football isn't absolutely decisive in that way, but United's limited role in the Champions League post Ferguson means he has left little imprint in the European game leaving more at stake on how he performed with Spain. When you compare him with the all-time goalkeeping greats (which is where he should be compared given his ability), just about all have impressive international careers (Buffon, Zoff, Shilton, Jennings, Dasayev, Yashin) or inspired major tournament showings (Schmeichel, Kahn, Toldo, Maier, Mazurkiewicz, Preud'homme, Chilavert) to their names.