Quite frankly, I assumed everyone knew that the average save percentage had changed between the 1970s and 2010, so I didn't take the question seriously. But in case you didn't, the average save percentage jumped by .2, from .890 to .910 over that period.
Dryden is not a comparison point. His career is like if Thomas came into the NHL, had his first season in 2009, replicated that performance in 2010, had his same performance in 2011, then followed it up with a 2-3 better seasons, before retiring to become a lawyer.