Much of the pre-fight talk before the rematch centered on the animosity between the two and their harsh words toward each other.
Golovkin came into the fight undefeated at 38-0-1, while Alvarez had lost only once, to Floyd Mayweather.
The Mexican blamed the test failures on eating contaminated meat in his native Mexico.
To his credit, he played it all perfectly, especially Saturday's 12 rounds.
There was plenty of enthusiasm heading into last September's fight between Canelo and GGG, which included some memorable moments and flurry of punches.
The fight came after an acrimonious weigh-in during which Alvares nearly head-butted Golovkin, who is known affectionately through the boxing world as "Triple-G".
While Golovkin appeared to take issue with the result, there was little sense of controversy about Saturday's outcome. Golovkin reportedly says he wants a third bout with Alvarez. Oscar De La Hoya has promised that the main event will start no later than 11:00 p.m.
"One of the best fights I've ever seen", tweeted James. "Unfortunately we didn't get the knockout", he said.
It was about as close as could be, too. Golovkin's jab began to find its' range and he finished the stronger of the two men, but each round was so close.
Lemieux lands a left hook with two minutes and 44 seconds remaining of the first round and O'Sullivan struggles to stand.
Fingers crossed a third fight comes to fruition for the pair in May 2019.
Panthers open season with 16-8 win over Cowboys
But since the day wasn't over, Bryant wasn't finished taking shots at his former team. The Cowboys did not play well in their 16-8 loss to the Carolina Panthers on Sunday.
Golovkin threw and landed more, according to CompuBox, but Alvarez landed at a significantly higher percentage. But judges Dave Moretti and Steve Weisfeld each saw it 115-113 for Alvarez, giving him the win and handing Golovkin his first defeat.
Sanchez, meanwhile, brushed off suggestions that Golovkin had once more been on the wrong end of a dubious performance by the three ringside judges.
He was approached on a couple of occasions to discuss the fight but was clearly not having it.
'That's what Golovkin made Canelo do tonight.
"I'm very emotional. That's what I did". The bad news is this is boxing, and business has a way of mucking up the simplest of plans.
His mother was pictured praying at ringside after a ninth round which saw both men launch repeated attacks and Alvarez nearly came unstuck in the 10th as a left hook to his jaw briefly rendered him limp, only for him to somehow instantly find poise.
Golovkin, who had yearned for years for a big-time fight, had knocked out 23 consecutive opponents at one point before winning a highly competitive unanimous decision against former middleweight titlist Daniel Jacobs in March 2017 before agreeing to fight Alvarez.
Alvarez now finds himself in rarefied air, perhaps the biggest name in a sport desperate for a transcendent superstar.
Could the fight have gone either way?
Both fighters were cut during the bout, with Golovkin receiving eight stitches for a cut around his left eye. His mood, though, was light. We can't take that away from Canelo. "I'll be back guys; I'll be back".