It all depends if you have a timeline involved. If you say throughout their career who is the best all around skier, I would argue for Candide's sake but give Tanner a very close second. Both have all three X-games golds, both have got gnarly over Chad's, but I give the edge to Candide on slaying backcountry and AK style lines. He just skis better than Tanner in that aspect.
All the other people saying best well rounded skier is Delorme or Tudor, man, not a chance. Both of them are amazing skiers, but neither have the kind of results that Candide or Tanner have, although Dane has some good freeskiing results for sure. Same goes for Sammy, one of my favorite skiers, but seriously, not the craziest lines as much as big bc booters and tricks off cliffs. Sage kills all of them on AK, but certainly is smoked out by most of the aforementioned names in park. Seriously, Sage killing it at X-games? Please. I'd much rather see him toss some floaty flat 3's over natural gaps anyway.
Thanks for reading, have a great day.