The real Reagan presidency is a lot different than the myth.
-Gets credit for ushering in deregulation, even though it was already well underway with Carter.
-Gets credit for the big right-turn in US politics, even though it didn't really happen until the mid-90s.
-Gets credit for things that haven't even happened like dismantling the social safety net. When in fact, Reagan actually strengthened Social Security and Medicare.
-Raised taxes countless times
-Granted amnesty for illegal immigrants
-Signed a gun control bill
He angered many hardline conservatives with his centrist/pragmatic domestic and foreign policies.
I think the conservative god myth started due to exaggeration from the left and right - as well as Republican nostalgia for a time when a Republican president was really personally likeable, charismatic with strong conservative rhetoric and fairly popular (even widely so at certainly points).