Jose Altuve’s towering home run to left field was the lasting vignette of Monday’s 6-1 win over the Royals, with Altuve rounding the bases and passing in front of the Royals’ own second baseman, Omar Infante, as the Astros cruised to begin a three-game series. Everyone already knows Altuve — who already has as many homers as he did last year, seven — is more deserving of a starting All-Star bid, yet it’s Infante who’s presently leading the fan balloting. Monday’s shot was emphasis. Less clear is which club is the in the best in the American League, and these two have the best case of any. But it’s hard to reach much as far as the Royals’ ability goes because of the sloppy pitching of their starter, Joe Blanton. The 34-year-old Blanton, who came out of retirement after working at his California winery last year, allowed five runs in 2 2/3 innings, including Altuve’s leadoff shot in the third. When the Royals came to town for a couple of exhibitions just ahead of the regular season, it would’ve been hard to imagine this three-game set as a must-watch series. But it deserves that billing. (The 20,419 in announced tickets sold at Minute Maid Park suggests the designation may not hold true with Astros fans in the same way the well-attended weekend series with the Yankees did.) “We’ve been confident long before we’re given credit,” Astros manager A.J. Hinch said. “We don’t gauge ourselves against the Yankees or the Royals or any team we’re playing.” The Royals, who fell to the Giants in seven games in the 2014 World Series, have the American League’s best win percentage at .603 (44-29). That’s not a shock. But there are the Astros, with the AL’s second-best win percentage .570 (45-34), and the shine of surprise still hasn’t worn off for most people. It might not get better than these two teams.