Yes, I know you were talking about scoring, but I just wanted to emphasize - maybe redudantly? - that the top scorer is not always the best player/forward; Viktor Zhluktov in the 1976 Canada Cup would be a prime example... he might have gotten the most points, but he didn't really dominate anything (and of course I'm not comparing Zhluktov to Gretzky in any way!). Gretzky often won the scoring title by 1 point (1981 CC, 1982 WC, 1984 CC, 1991 CC...), so it's not like he always blew away the competition, points-wise or in other ways. Yes, he still proved that he was an excellent player in international competition too.
I'd say that the 1984 CC and 1991 CC are 'arguable', meaning that I'm not saying he absolutely 100 % wasn't the best player, but it is, as you said, up for debate. In 1984 John Tonelli was named the tournament MVP and in 1991 it was Bill Ranford. Whether 1991 should count or not (i.e. due to his injury), I don't know. WJHC I'll leave to someone who is better-informed.
Yes, the Great One had some big games in the 1982 WC, and he got better and more efficient as the games got tougher & more important, but still I don't think it was enough to make him the best forward/player in the tournament; Viktor Shalimov was named the best forward, and there were the likes of Makarov and Kapustin who were more consistent, I think. Fetisov was dynamite on defense. I'm hearing arguments like "it was a totally different situation for Gretzky!", but we were talking about whether he was the best in the tournament or not. If my memory serves me right, Bill Barber and Gretzky formed a nice tandem in the WC. Bobby Clarke was awful. It was during the 1982 WC, I think, when Anatoly Tarasov praised Gretzky's 'hockey intelligence', calling him "the smartest player I've ever seen" or something like that.
I hope this isn't Gretzky-bashing