With only two years to evaluate it's damned hard to arrive at a conclusion.
I think the fact that he took us closer to nuclear war than any other POTUS (since FDR, of course) doesn't make him look so good, though.
The fact that we didn't go to war, does mitigate that complaint somewhat.
The BIG BIG question is, what would he have done in Viet Nam?
We'll never know, but we know what Johnson did, and that was totally screw things up.