Overtimes

[ProfessorBen]

I'm not sure on all of these so correct me if I'm wrong.

MLB - An extra inning is played until 1 team is ahead of the other.

NBA - A 5 minute overtime period is played beginning with a jumpball. No additional personal fouls are allotted. Teams get 2 60-second timeouts and 1 20-second timeout. Overtimes continue until someone wins. 4 team fouls result in free throws.

NFL - Regular Season: 15 minute period. Coinflip leads to one team getting the ball. Sudden Death, first team that scores wins. If the period ends without anyone scoring, a tie is given to both teams.
Playoffs: Same as regular system but they game is continued until someone scores.

College Football - One team starts with the rock at a fixed point and gets 1 possession to score. The other team repeats and tries to match or beat that. A tie leads to another overtime. In the 3rd overtime and after, teams must attempt a 2-point conversion after scoring a touchdown.

NHL - Regular Season: A 5 minute sudden death overtime is played 5v5. If tied at the end of this period, a shootout begins with 3 players on each side taking a penalty shot and continues until 1 side is ahead in a round.
Playoffs: 20 minute periods are played at full strength(6v6) until someone wins on the first goal made.

What makes a good overtime? Which of these systems get it right? What recommendations do you have for fixes? Are changes between regular season and playoffs necessary or worthwhile?