Bud Selig has been commissioner of baseball for 20 years now. Oh, how time flies. Unfortunately for him, I believe he'll be remembered primarily for two things: the strike of 1994, and performance-enhancing drugs. Let's look at his whole tenure though...
1994. It starts, of course, with the work stoppage of '94, which ended the season in August. I'll never forgive him for that (neither will many Canadians). The Yankees were the best team in the AL (70-43) while the Expos were the best in MLB (74-40). Due to the strike, it was the first year without a World Series since 1904. It was Don Mattingly's best chance to win a ring. The effects lasted for years afterwards; it led, indirectly, to many of the following changes.
1995. "Realignment into three divisions in each league and the Wild Card." This enabled the Yankees and Rockies to play in the postseason. Despite that, I wasn't (and never will be) a fan of this. If the need is to have more teams in the playoffs, why not eliminate the divisions, balance the schedule, and welcome the top four teams in each league into the postseason? There are so many reasons this is superior to the current format (but I can't go into that now).
1997. Interleague play during the regular season, something that only existed in the All-Star Game and World Series before. I don't have strong feelings either way on this. It's nice for fans to see stars of the other league now and then, but for every Yankees-Mets, White Sox-Cubs matchup, there's two more that mean nothing (Pirates-Mariners, Marlins-Rangers, etc.)
1998. Two franchises added: the Arizona Diamondbacks and the Tampa Bay Devil Rays. Another "meh" decision. It waters down the overall quality of play, but it gives two apparent "baseball towns" teams to root for. We see now, though, that no matter how good Tampa is, the fans won't show up (they haven't ranked higher than ninth in the AL in attendance since their first season).
2000. Putting all umpires into a ML pool instead of having a separate pool for each league. The first all around good decision. There should be uniformity among officials.
2001. Unbalanced schedule introduced. Awful. Gone are the days of rivalries with none division teams. I actually remember when the Indians, Tigers, Mariners, A's, White Sox, and others were serious rivals of the Yankees. Not anymore, now that they play four teams 72 times every year.
2003. "Home field advantage in the World Series granted to the winner of the All Star Game." Idiotic or most idiotic decision of Selig's tenure? Is awarding it to the team with the best record not complicated enough? While this change was supposed to increase interest in the All-Star Game, TV ratings have continued to dwindle, reaching all-time lows the last two years.
2004. "Transfer of Montreal Expos franchise to Washington, D.C., becoming the Nationals." Insult to injury. In addition to ending Montreal's season early in '94, Selig took away their ball club in 2004. While I think it had to happen at the time, the strike that originally sparked it could have been avoided.
2005. Stricter performance-enhancing drug testing policy. Good, I guess. I honestly don't really care about amphetamines and injury-recovering therapy (e.g. HGH), but anabolic steroids are too far, in my opinion. The Mitchell Report, however, was a joke. It focused mostly on just a handful of teams and named some players while not naming other users. It gave tacit innocence to everyone not in it. It should have named every single guilty player or none at all.
2006. World Baseball Classic. Does any American care? Unless the best players actually partake (like in the World Cup), what does it matter? Make it every four years and ensure the top players take part. Then, perhaps, interest would be there.
2008. "Introduction of instant replay in the event of a disputed home run call." His best overall change. Unfortunately, things like this have been few and far between in the Selig Era. Now if we could only get technological assistance on strikes/balls and safe/out calls.
1992-present. A lot of new stadiums have been built. I commend Selig for motivating(?) this, as it's given rise to many beautiful ballparks and increases in attendance. We have yet to see, though, how long it will last. Honeymoons aren't forever.
There's a lot of bad in there. I don't believe for a second that the owners (and therefore Selig) didn't know about the rampant PED use in the late 1990s. For him to act all high and mighty about it after the fact was incredibly hypocritical.
There is, however, some good, like the implementation of video review and the inclusion of umpires into a single group.
So... what's been his greatest legacy and his biggest mistake?