Straightforward question.
Houston
Thought to be a title contender at the start of the season with the addition of Lawson and the return of the majority of their roster from last year (minus Josh Smith, who they now have back), which went to the Western Conference Finals. Lawson clearly didn't work out. Fired McHale after a slow start, but their current coach definitely isn't any better. Currently they're just 1 game above .500 with a 33-32 record in a Western conference that is much weaker than last year, and don't project to be a true playoff threat in the West as expected.
Milwaukee
Supposed to be a team on the rise with their youth and size, at minimum thought to be a playoff team this year. Giannis heading into his 3rd year, Parker getting healthy off of his ACL tear, and Middleton was resigned after a solid previous year. Added Moose who was a highly coveted free agent. Currently they're just 27-38 with major defensive issues (defensive rating 105.6, 9th worst in the league) and will not make the playoffs this year.
Washington
After a decent playoff run last year, Washington has underperformed this season. Beal has been injured, but Wall and Beal form one of the most formidable backcourts in the league. They have a decent mix of youth and veterans. Although they're just 2.5 games from the 8th seed, a 30-34 record is less than impressive and they probably don't pose a threat to the better teams in the East if they do happen to make the playoffs.
Chicago
Obviously the injury to Butler was huge (as well as Noah being injured), but I personally can't help but be disappointed with Chicago. After being one of the best defensive teams last year under Thibs (top 5, if I'm not mistaken), they've regressed defensively and are still one of the worst offensive teams in the league (offensive rating 100.9, 5th worst, just ahead of Brooklyn), something that Hoiberg was supposed to help address. They're also constantly collapsing in the 4th quarter. According to a Bulls fan, the Bulls have the 3rd-worst net rating in the NBA at -6.5 since February 1st, with only the Suns and Sixers being worse. The Bulls are just at. 500 (32-32) and will miss the playoffs if they don't get their act together soon.
Honorable Mention
New Orleans - injury-riddled season, but they shouldn't be as bad as 24-40. There's enough talent on that roster to do better than that.
My vote:
Houston, although I never counted on Houston being a true contender because the addition of Lawson wasn't sufficient to make them favorites over Golden State.
I think Houston will probably have the most votes just because of expectations, but in my opinion Milwaukee is just a hair behind. I expected Milwaukee to be at least a 6-8 seed this year and see them as a highly underperforming team. Just goes to show you how important chemistry is, both in Milwaukee's case and also for Houston, who has two superstars that don't like each other.