As a historian and student of 20th Century US History, this event is as much as a major milestone event as the attacks on Pearl Harbor, HI on Dec. 7th, 1941 and NY-PA-Wach. DC on Sept. 11, 2001.
I never really thought JFK was a good president. He screwed foreign affairs pretty badly and as many enemies within the US as outside it. I do give him credit for lighting the sparks that would lead to NASA and the Peace Corps.
As for his death, I do believe he was taken out by a combination of the CIA, FBI and US military. They saw him as a threat to national security and then-civil rights policy. I feel that Oswald was a lone nut who did get a lucky shot off at him, but it was person(s) unknown who(m) actually killed him. I feel that the federal government had to cover-up everything so to better secure US VP LB Johnson (D-TX)'s rise to the presidentcy.
Lastly, I don't think we will ever know what really happened. But maybe it really doesn't matter any more.