2014-2015 version of Caludio Bravo to me is still the best keeper that we had in recent years.
That being said, Alisson is currently #1 and Stegen is among the top 5, much better than Valdez was on average.
Valdes last season 1,5 here was Bravo 14/15 on a different level, at that time he was our second best player iirc bar Messi - and our team was better back then and not comparable to ter Stegen being second best here for moments/a period. Valdes was just that good, and made me see him in a different light. ter Stegen hasn't had a whole season where he looked unbeatable, he had that 4-month period a while back, but it was more in de Gea greatness with being superior on the line plus passing skills. I have never seen that total domineering aura from him which all great GK have had... Valdes had it in his last years here. Schmeichel, Neuer and Kahn were like that. Casillias, van der Sar and Alisson also had/has that "unbeatable"-vibe over a whole season(s), but not that domineering aura. ter Stegen will probably be in this second category if he could take the finale step. He has the talent and work ethic to reach those heights, but I think there is a pschyolgical barrier he needs to break which may be difficult. Look at Messi he never took that step to leadership. MatS has the desire and talent to make the finale step into best Gk category and put responsibility on his shoulders, but despite him being "cultural responsible" for barca and catalonia, he still often looks apart from the whole. Like he isn't tottaly accepted by the seniors Pique, Sergio, Messi, Suarez and Alba (follower-attitude). His voice is respected in politeness because of his level but not to an extend he is allowed to get into leadership position. That Sergio Roberto is voted 4th captain ahead of ter Stegen says it all. The guy has been groomed by his colleagues and still looks like a wimp. In ter Stegen I could see Actual leader potential. If it were a German club I'm sure he would be bossing it around.
Well my thoughts kinda drifted, but some thoughts I have had on ter Stegens situation here.