He blossomed as the right winger on the famous G-A-G Line (Goal-A-Game) with Jean Ratelle and Vic Hadfield, and although he never played on a Cup champion, he was often at his best in the post-season.
An amateur scoring star with the OHA's Guelph Biltmore Mad Hatters, Gilbert was part of a Memorial Cup triumph in 1959-60. In 1960-61, when the team was renamed the Royals, Gilbert led the OHA with 54 goals and 103 points. He came close to winning consecutive scoring titles but lost the scoring crown to Chico Maki on the last day of the 1959-60 schedule. Gilbert had just received word that he was an emergency call-up to the Rangers when disaster struck. In the last junior game of the year, he skated over some debris thrown on the ice that caused him to fall awkwardly into the boards. The impact resulted in a broken fifth vertebra in his back. To repair the damage, doctors removed bone from his left leg and used it to bind the fourth, fifth and sixth vertebrae together.

After recovering from his injury, Gilbert gained some professional seasoning with the Kitchener-Waterloo Beavers of the EPHL. On November 27, 1960, he made the most of a one-game call-up to the big leagues by assisting on Dean Prentice's third-period goal that gave New York a 3-3 tie with Chicago. Following an injury to Ken Schinkel, Gilbert was an emergency recall during the 1962 semifinal series against Toronto. He didn't look out of place and contributed five points in the four games he played with linemates Dave Balon and Johnny Wilson.

Gilbert finally made the team outright at training camp in 1962. He scored 31 points as a rookie, then registered his first of 12, 20-goal seasons in his sophomore year. Gilbert was a deceptively fast skater with an ability to elude many of the league's wiliest checkers. He was blessed with a hard shot that often dipped and he didn't shy away from battling hard in the corners or in front of the opposition net.

Meanwhile, the surgery Gilbert underwent wasn't totally successful. The bone graft loosened over time and eventually disintegrated as a result of the bodily contact so common in hockey. Prior to his third season, it was discovered that the surgically repaired vertebrae were damaged and required further attention.

He tried to play the 1965-66 schedule by wearing a special custom-fitted brace, but the extra equipment affected his breathing and, to some extent, his stamina. In January 1966 he was forced to abandon the season and undergo an operation to save his career. Gilbert came through the surgery and rehabilitation well and scored 28 goals the next year when he led the Rangers into the playoffs for the first time in five years.

It was in 1970-71 that he began playing with Ratelle and Hadfield. The line clicked and helped the Rangers set a franchise record of 107 points. The following season Gilbert set personal bests of 43 goals and 97 points and helped the team reach the Stanley Cup finals. The line made history by becoming the first on which all three members reached the 40-goal mark. Additionally, all three finished in the top five of the NHL's scoring race. Flying down the ice with elan and purpose, Gilbert caught the imagination of Manhattan's sporting public. His movie-star looks and love of the nightlife made Gilbert a natural fit in the Big Apple.

During the Fall of 1972, Gilbert represented Canada in the Summit Series against the USSR. His desire to play for Canada was so great that he ignored the many overtures that were sent his way by teams in the newly founded World Hockey Association. Between 1972 and 1977, he scored at least 75 points five straight years, but the Rangers never made it past the semifinals. On March 24, 1974, his goal against Dave Dryden of the Buffalo Sabres made him the first 300-goal scorer in the history of the New York Rangers. In 1976 Gilbert was presented the Bill Masterton Memorial Trophy as a tribute to his dedication on and off the ice.

On December 12, 1976, he celebrated his 1,000th game by setting up three New York goals in a 5-2 home-ice win over the Stanley Cup champion Canadiens. Gilbert was also on hand when professionals were allowed to take part in the 1977 World Championship. He and linemates Walt McKechnie and Guy Charron helped Canada finish fourth in the historic competition. Before the start of the 1977-78 season, Gilbert was engaged in difficult contract negotiations with Rangers general manager John Ferguson. Following a 15-day holdout, Gilbert never really got going and only lasted 19 games before retiring. His output totaled 406 goals and 1,021 points along with a host of New York scoring records.

The classy winger was elected to the Hockey Hall of Fame in 1982.