Despite being part of the All Blacks squads that claimed back-to-back World Cups, on home soil in New Zealand and then England, Williams said an Olympic gold medal would outrank those achievements.
"I guess it would have to surpass it because as an athlete there's no higher level than the Olympics," said Williams, whose sister Niall will turn out for the New Zealand women's team in Brazil.
"I'm just fortunate enough that (coach) Titch gave me a shot at the start of the year, to learn off the team and train my butt off. We just want to be successful."
He added: "I always knew it was going to be tough, but it was really hard.
It's a totally different game to 15s.
"There's been a lot of 15s players who've tried to make the sevens team but they haven't made it because it's a totally different game. That's why I'm thankful I sat down with Tich at the start of the year and we sussed out a plan to put me forward for the whole year to try to crack it."
Veteran sevens player Tim Mikkelson said Williams had proved any sceptics wrong.
"When he first came we didn't know what to expect," Mikkelson said.
"He's very physical in the games and in training. He's just improved in every training and his fitness has got better."