It can be reasonably argued that Gilmour was the third best player on that team, if not fourth.
Is there a single season that Sundin had a cast close to that?
You do realize Sundin was part of conference final teams too (2 in fact) with the Maple Leafs. Gilmour was a fantastic Leaf and his peak is sure an argument with Sundin's on the roster and he's a good debate whose the better overall player but in terms of who was a better overall Leaf, you can't take Gilmour's two great years over Sundin's entire tenure.
And you assume Sundin didn't have a desire to win. His 15 overtime goals disagree.