Yeah, it's worth noting that all presidents always look better in retrospect than when they're in office. Not that Obama is doing a good job as president or anything -- he's clearly not.
Death has a lot do with it. Obama is worst and Reagan is best numbers in this poll are driven by 65+ and 50-64. Bush is worst and Clinton is best is the under 50 consensus. That's going to be the opinion of the history books
this generation will be in charge of writing. That's how it works.
Older people did not like Ronald Reagan in the 1980s. He was anti-New Deal, anti-union. They remembered him being anti-Medicare in the 1960s. They were fearful. Carter and Mondale won the senior vote.
But the 50-60 year olds of today were the young adults of the 1980s and cast their first ballots for Reagan. Even the 60-70 year olds who came of age post-Watergate could look to Reagan as their first President who was Presidential.
It's a never ending cycle.