Two additional points. 1) The mixture of player ability is mostly due to cost penalties for paying players a higher salary (although Yankees just pay it). Not as distributed as (american) football, but still distributed. 2) Note the longest winning streak is 26 games out of 162... out of 162. Longest basketball streak is 33 games (not enough for an undefeated 82 game season). The ability to have a 162 game streak that starts on game one and lasts through the baseball season is essentially impossible. It is possible to have an undefeated season in american football where the season is 16 games (but it is rare -- hasn't happened since pre-NFL 1937, 1948). Baseball has an order of magnitude more games per season.

EDIT: I knew that wasn't right (that's what I get for haphazardly scanning Wikipedia for facts). A couple others since recently 2007 Patriots and 1972 Dolphins also had undefeated seasons in NFL. Still rare, and still a fraction of the number of games. Point is: luck is only part of it, no matter the sport staying undefeated is difficult -- especially for a season when season means 162 games! Thanks for pointing out the mistake everyone. Sorry for the confusion!