Well, you have to remember that what happened was essentially a perfect storm of bad luck. Reagan's gambit was exposed - which honestly he probably gets away with 99 out of 100 times back then, it wasn't the internet age or anything. Not only that, it explodes into a bigger and bigger scandal constantly, consuming his presidency when in a lot of cases, it would've died off in time. Reagan was a charismatic president who really had a way with words, but somehow he never found the right words to deal with that particular crisis. Rather astonishing when you study him beyond that one scandal, as it's like he was a different person dealing with it. Let alone the fact that the public and press just wouldn't let go of it, even when other stories broke. Simply stunning, really. Maybe God voted Democrat in '80 and wasn't happy with the outcome, I don't know, since it sure seemed like the 80s were set to be a Republican decade.
I honestly think Reagan would've been a solid president, probably a two termer with the incumbency advantage. He was a swing to the right, but the conditions were there to recover from the 70s regardless of what you think about his economic policies. He would've taken a hard line with the Soviets for sure, probably accelerating the decline of the Sovs and leading to an earlier collapse than '91. Domestically, he might've handled the AIDS crisis better than Mondale, maybe not. That one's tough to say since it sort of surprised everyone. No universal healthcare I imagine and probably economic and regulatory looseness instead. More than anything else, I would expect him to do all of that and do well with his excellent communication skills, which would paper over a lot of flaws.