The guys over at 538 have proved the Cubs really are the unluckiest team in baseball—but they still give them a 48% chance of winning the World Series:
[A]ny ballclub that appears in the postseason often enough — no matter how mediocre its teams are — should eventually be guaranteed a World Series win. But for more than a century’s worth of Cubs squads, no level of greatness has been able to get them over the hump. I determined just how unlucky each franchise has been over its postseason history by taking its Elo rating and the size of the playoff field and then calculating how likely the team was to win the Series each year using the process I outlined above. I added up those probabilities from all the years in which a World Series was held and compared them with how many titles the teams actually won, and I found that the Cubs are the unluckiest team of the last 113 years.
Just based on the pretty-good teams the Cubs have featured in their 18 playoff appearances, my model expected them to win six or seven championships. Instead, they’ve only won two since 1903, and both were more than 100 years ago. (Notably, this year’s Cubs triumphed in the NLCSover the second-most-unlucky team, the Los Angeles Dodgers.) The Cubs have had more years to be unlucky than most teams, since they’ve existed for a long time. But even on a per-playoff-season basis, the Cubs have been the least fortunate franchise in baseball.
That said, the Cubs are in Cleveland tonight to play their first World Series game in 71 years. Will they win it all? No one can say. But they're here.