Creativity is spot on, that is his greatest asset.
Most people say speed is Connor's primary attribute, which of course makes sense being the fastest player in the league with and without the puck, a rarity that only a handful of players in NHL history possessed. That's what everyone sees on the daily highlight reels, McDavid picking up the puck in the d-zone, flying through the neutral zone, out-skating premier defenders and finishing the job.
But Oilers fan's know, watching him game by game for over 3 years now, that it's his intelligence and intuition that makes him who he is. His ability to create something out of nothing, on a consistent basis, in both the defensive and offensive zones, is what makes him a generational talent. He's so smart in high-pressure situations, rarely flustered and his anticipation on what the opposing player(s) will do and then making a play based on that, is pure genius.
A clear example of his hockey IQ in a game this season, was the entire play on the overtime goal vs Boston on October 18th:
3v3. The Oilers defenseman takes the puck behind the Bruin's net. Patrice Bergeron sees Klefbom, Draisaitl, Marchard and McAvoy battling behind their net and starts skating towards the Oiler's zone in anticipation that they'll win the battle and make a stretch pass for a breakaway. He was right, Marchard won the battle, both Klefbom and Drai are well into Boston's zone and Marchard makes that stretch pass to a speeding Bergeron for the easy breakaway. Oops, intercepted by McDavid, makes a move around Marchard and sets up the game winner on a 2 on 1.
Rewind, McDavid also saw the battle behind the net and also anticipated the stretch pass, so he follows Bergeron, after he turned around and started skating towards the Oilers zone. But if you watch the overhead view, McDavid stays a couple feet to the right of Bergeron, staying out of his area of vision, making it seem he's alone and that Marchard has a clear lane. He baited it, as soon as Marchard released the pass, McDavid made a sharp left turn, with 3 quick lunges towards the passing lane and stole the puck.
To me, that is just him on another level. As the saying goes, he's playing Chess out there while everyone else is playing checkers