Here’s a graph on the political ideology of post-war presidents. Note the scale to the left; Republicans are twice as conservative as Democrats are liberal, in general.
This sort of political analysis is normally fraught with problems, although these researchers have taken steps to reduce some of them and to make this analysis work over time. It’s hard when liberal and conservative are terms that are defined within the context of legislation that actually gets presented, but it’s a starting point.
The take-away is that Republican presidents are more conservative than ever, and that Obama is the most conservative post-war Democratic president.