Clint Eastwood -- We Haven't Had a Great President Since Truman!

Clint Eastwood tells TMZ ... he hasn't been impressed with an American president in quite a while ... dating all the way back to one Harry S. Truman.

Eastwood was leaving the Beverly Wilshire hotel this weekend -- where Obama stays when he's in town -- when we asked the Hollywood legend to pick his favorite U.S. president of all time.

Clint said he was a big fan of Washington and Lincoln and then asked, "You mean in our life time?"

Eastwood then explained, "I think Truman because he got mad at the people who bum wrapped his daughter."

But then Clint dropped the DISS -- saying, "We haven't seen one for a while."

So, we gotta ask ...