Romain Grosjean in a Lotus was second 2.5 seconds behind and Sergio Perez in a Sauber was third, followed by Red Bull's Sebastian Vettel.
"I think this mix-up is normal. I think this is going to be normal for this season," he said after winning his third Canadian Grand Prix. "I think it's great for Formula One. It's great for fans today."
Hamilton won in 1 hour, 32 minutes, 29.586 seconds, taking advantage of fresh tires courtesy of a second pit stop while the other contenders only made one.
"I had so much traction with fresh tires," said Hamilton, who earned his first Formula One victory here in 2007 and won again in '10. "I wasn't able to do it in a one-stop. I think I would have fallen farther back, as they did. I think a two-stop was just right."
Defending Formula One champion Sebastian Vettel of Red Bull was fourth and Fernando Alonso, who won in Malaysia and came into the race atop the driver standings, was fifth.
Last year, Vettel won five of the first six races and was in control at the Circuit Gilles Villeneuve before a last-lap skid in the rain allowed Jenson Button, Hamilton's teammate, to pass him for the victory. Vettel went on to win 11 races and the Formula One title in 2011.
But this year's championship has thrown up a new winner every week: Never before had there been even six different winners to start the season. Hamilton made it seven on Sunday, taking a two-point lead â€" 88 to 86 â€" over Alonso of Ferrari.
"We've got a win and 25 points, but we've only got a two-point lead," Hamilton said. "It's incredible how close it is. I think it will stay that close throughout the year."
A year after the longest race in Formula One history â€" a rain-delayed affair that lasted more than four hours â€" there was no appearance from the safety car. Hamilton, who dropped from first to third when he made his second pit stop on the 50th lap, was fastest on lap 59, then passed pole-sitter Vettel on lap 62 and Alonso two laps later to take the lead.
Grosjean and Perez stayed with him, but they were unable to close the gap on their well-worn tires.
"We went aggressive," said Perez, who finished second in Malaysia on March 25. "It's a great boost for the team. Every podium is special, especially when it's only your second podium in Formula One."
Grosjean had said the Circuit Gilles Villeneuve was his favorite track â€" even though he did not race in Montreal in 2009, his previous Formula One season.
"It's true that on video game it's my favorite track," he said. "It's more bumpy than the Xbox, sitting on my couch."
This year's race marked the 30th anniversary of the crash that killed Villeneuve, the local favorite whose success helped create the track that is named after him. Fans wore T-shirts that said, "Salut, Gilles," and the car he drove in 1973 took a ceremonial lap before the race.
Across the bridge from the Ile Notre Dame in downtown Montreal, students continued their protests over planned tuition hikes. One anti-capitalist group vowed to disrupt the race by overloading the subway to keep race-goers from the one of Canada's most lucrative tourist events.
Police spokeswoman Anie Lemieux said about 30 people were arrested at the subway stop near the race track as a preventive measure. Others had their bags checked and were turned away if they could not produce a ticket to the race.
On Saturday night, police in riot gear blocked off streets in an attempt to keep the students away from Formula One revelers, who felt a faint sting of pepper spray as they sat on restaurant patios and watched the protests go by.
