Of course we should. Reagan pretty much created the current GOP's unholy axis of fundamentalist lunatics, neo-con warmongers and crackpot pseudo-free market 'tax cut' fanatics. Also Bush is pretty much the logical conclusion of the party embracing his optimistic (to the point of being self-deluding), 'facts are stupid things' philosophy of politicking.
There's nothing wrong with optimism. Ever hear of seeing the forest for the trees? Sometimes focusing too hard on 'facts' can have that effect on people. That's not to say that facts can be ignored of course, but one must always approach forward thinking with an
a priori positive bias. How many people thought that communism could be defeated? In that sense Reagan and FDR were alike; they both emphasized the power of positive thinking, while remaining maturely grounded in reality that showed in more quiet, subtle ways.
I do agree with your broader point though; Reagan is such an important historical figure in creating what the GOP is today that anything it has become undeniably bears a large part of his fingerprint. The dark side of Reagan was always his uncompromising ideological stance and the excesses of the movement that backed him. When Reagan left office, he took with him the charisma, the sunny optimism, and the powerful synthesis of man and history that fit together well in that decade of the 1980's, but bequeathed on the nation a strong, mature political movement of conservative reaction convinced of its righteousness and willing to go very far to get what it wanted.