I was too young at the time to really understand what policies Kennedy and Johnson supported. By the time Johnson was elected, I had formed an opinion of him that he was a rattlesnake. I based that on his escalation of the Vietnam War and his Great Society programs, not to mention his likely involvement in JFK’s death.
JFK was a mess in his personal life, but did not seem as far to the left on Vietnam. Bobby was better than either of them in a lot of ways.
I think Reagan and Bush agreed on the bigger issues, as did Carter and Mondale before them. I also think Obama and Biden are simpatico.
Were you even around at that time? Reagan and Bush couldn't have been farther apart on the issues. Bush called Reagan's plan for the economy "voodoo economics". Their joining together was a shotgun wedding, arranged at the last minute, because that GOP powers-that-be wanted Reagan to accept a Reagan-Ford ticket (a "co-presidency"), which Reagan absolutely rejected.
GHW Bush was downstairs in a bar, drowning his sorrows when operatives came looking for him. The shotgun wedding was arranged: he was to be the Veep. Reagan accepted Bush as a last-minute compromise. Nancy Reagan mistrusted the Bushes from the outcome.