Depends on the criteria... this could delve into MVP arguments on a team scale. Are the Red Sox the most successful for finishing dead last more times than they won it all? Consistently qualifying for the postseason is a factor, but winning some playoffs has to count, too (as does going 16-2 vs. the Twins, Yankees...).
Houston is definitely #1 the past decade, and though it's easy for some to trash the Astros, it also took losing over 100 games three years in a row to get there. New York has won the most games and made the most playoffs, but most of its true glory came at the tail end of the dynasty from the 1990s. No Yankee fan would dispute this.
In between are two model NL clubs with the best unis: Dodgers and Cardinals. Both have deep farms they don't decimate when trading for stars others can't afford (like Boston once did, for Pedro and Schilling). LA can also buy anyone it wants, and in this century, has had two losing seasons... but St. Louis has only one. Dodgers won one ring in a pandemic... Cards won two. I vote St. Lou.