2010, 2007
It's a bit subjective to say which St. Louis Blues draft class was the "best." Do you go with the class that produced one of the no-doubt best players, but little else? Or the one with numerous players getting significant NHL games, even though they lack the star power or scoring? The draft class with the most total points? And that's before considering different NHL eras and how the game's evolved over the years.
For the purposes of this, we're going to go with a class that produced players with staying power who remained effective for much of their careers. There may be a bit of recency bias at play, but the NHL after 2004-2005 lockout is arguably the start of the current era, and we see a bit of stability in the draft--no more double-digit rounds like in the 1990s.
Before we get into the winner, a shoutout to the runner up: the 2010 draft. With the 14th and 16th overall picks, the Blues picked Jaden Schwartz and Vladimir Tarasenko, respectively. Schwartz and Tarasenko have both played in over 800 games--and still going strong!--and Schwartz has 222 goals and 527 points, while Tarasenko has 304 goals and 662 points. Most importantly, both were key contributors to the Blues' Stanley Cup Championship team in 2019. Now, withour further ado, the best draft class the Blues ever had: 2007.
There was a lot of wheeling and dealing at the 2007 draft for the St. Louis Blues. They traded back from 9 to 13 with the San Jose Sharks (who took Logan Couture), and selected center Lars Eller. Then, the Blues traded up from 24 to 18 with the Calgary Flames (who took Mikael Backlund) and the Blues drafted defenseman Ian Cole. Earlier in the season, the Blues had traded Bill Guerin to San Jose for a package that included Jay Barriball, Ville Nieminen, and what ended up being the 26th-overall pick--and that turned out to be winger David Perron.
Eller, Cole, and Perron have a combined 3,198 NHL games, 542 goals, and 1,418 points; Eller and Perron both have well over a thousand games under their belts, and Cole isn't far behind with 908. The three players share four Stanley Cup rings, too: Eller got one with the Washington Capitals, Cole got two with the Pittsburgh Penguins, and Perron won with your very own St. Louis Blues in 2019. That's three exceptionally accomplished players in a single draft--a single round, even! It's just a shame all three couldn't have found their success in St. Louis, with only Perron winning with the Blues.
The Blues have draft classes with more star power behind them, sure, and more recent classes haven't had a chance to make their case (looking at you, 2023), but nailing three 1st-round picks in 2007 is enough to name it the best overall draft class the Blues have had.