Teams with at least 4 World Series appearances, the Pittsburgh Pirates have the best winning percentage. 5 World Series titles in 7 Appearances, 5 -2 for a .714 winning percentage. Teams with at least 10 World Series appearances, the New York Yankees have the best winning percentage. 27 World Series titles in 40 Appearances, 27 -13 for a .675 winning percentage.
because the world series
More than half.
Game 1 winners have a 367-164 advantage for a 69% chance of winning the series.
As far as MLB is concerned, winning percentage doesn't really enter in to whether a team makes the playoffs or not. A team makes the playoffs by winning their division or being the team with the highest winning percentage of those other teams that did not win their division. There have been teams to make the playoffs with a record as 'poor' as 83-78, as did the 2006 St. Louis Cardinals who went on to win the World Series. There have been teams with records as good as 94-68 (1982 Baltimore Orioles) that did not make the playoffs. That goes to show that a team with a winning percentage of just over .500 can make the playoffs where a team with a winning percentage of .580 can miss the playoffs.
The 1927 Yankees, arguably the greatest baseball team of all-time, had a winning percentage of .714 (coincidentally the number of career homeruns by Babe Ruth) by going 110-44. In 1998, they had a winning percentage of .704 with a won-loss record of 114-48. These are the only years their winning percentage was above .700. They swept the World Series in both of these years.
Yankees has the most world series win if that's what you mean. (27)
Yogi Berra played in 14 World Series with the Yankees winning 10.
There are seven games in the Major League Baseball World Series and the winning team needs to win the majority of the games meaning the winning Major League Baseball team will need to win four games out of the seven games in the series.