The third baseman went deep in his first three at-bats on Wednesday night - the first two off Justin Verlander and then a third against reliever Al Alburquerque - to get his name alongside Babe Ruth, Reggie Jackson and Albert Pujols in the record books.
Tigers ace Verlander lasted only four innings and 98 pitches as the Giants assumed control, charging into a 6-0 lead by the end of the fifth inning.
And they never looked like relinquishing their advantage, Barry Zito restricting Detroit to one run and six hits over 5 2/3 innings.
Sandoval told Fox Sports: "When you're a little kid you dream of playing in the World Series. And my dream has come true."
The 26-year-old Venezuelan felt the fact the Giants only secured their place in the World Series on Monday night - with a 9-0 victory over the defending champion St Louis Cardinals in the National League Championship Series decider - meant they hit the ground running.
"We played two days ago our last game," he said. "We had a day off yesterday and we came here still hot."
Detroit manager Jim Leyland accepted there was little his team could have done to keep Sandoval at bay.
"He just had one of those nights where everything we threw, he hit," Leyland said. "We have to tip our hats to him. It was unbelievable."