Astros should be #1. Yankees/Sox have better records, but Astros have a historic run differential per game and rate out as a ~110 win team. Record after 45-50 games is subject to more variance than run differential.

My top 5:

1. astros
2. yankees
3. red sox
4. braves
5. cubs

Kinda don't think any other team is close to those. Maybe the Indians, think they've mostly been unlucky so far, and maybe the Phillies/Nationals, but there is generally a large gap after those teams.