The Winnipeg Jets existed in the NHL for seventeen seasons. During those seventeen seasons, the Edmonton Oilers averaged 1.105 points per game, or 91 points per 82 games. In the fourteen seasons since the Jets departed for Phoenix, the Edmonton Oilers have averaged .948 points per game (normalized for the shoot-out), or 78 points per 82 games. While the Jets alone didn't account for the extra 13 points per season, they came damn close.
Not only were the Oilers 13 points better when the Jets were around, the Jets were key to each Stanley Cup run. Each spring, the Oilers took a turn beating the tar out of the Jets, propelling themselves deep into the playoffs by treading on the dreams of Manitobans. In fact, the Oilers have never won a Stanley Cup without beating the Winnipeg Jets first. The more time that passes without the Jets, the worse the Oilers franchise becomes. It's pretty clear the Oilers need an ugly duckling franchise in the division so that they themselves can stop playing the part of the ugly duckling.
So that, alone, should be one compelling reason to bring back the Jets. They are the Muttley to our Dick Dasterdly, the Porthos to our d'Artagnan, the yin to our yang. The Oilers without the Jets is an incomplete system, and it has gone on far too long.