The 28-year-old received criticism for initially moving to the Silver Arrows during the winter break, with many deeming the switch from McLaren as a step down.
However, Mercedes claimed third and fourth place behind the Red Bulls at the Malaysian Grand Prix, and Hamilton believes that only the reigning champions are superior to his current team.
"We are the second best team. To be that close — I was competing with the Red Bulls at some stages in the race — and to be in that position is a great feeling," said Hamilton.
"Unfortunately, we didn't have enough fuel in the car, more so my side. I was fuel-saving from lap 25 and it was very much an impossible task to challenge those up ahead. I was fuel-saving at the end like you would not believe: I was coasting everywhere. I'm sure if we were all on the same fuel it would have been a different situation, so I'm confident about that.
"I think this [Malaysia] proves that if we keep going in the direction we are heading, then there's a possibility that we could win a race at some stage this year."
Hamilton finished third in Sepang.