TWRoO on 13 April 2012
If we include high difficulty settings then it's probably the highest difficulty on The Conduit, closely followed by Deadly Creatures.
If using the default difficulty (which helps put more games on a level playing field, as some games don't have different difficulty settings) then I think Zack & Wiki gets top spot, perhaps tied with Toki Tori if that is allowable (it's on WiiWare so it is kind of this gen, but I think the same game may have been on GBC first, or at least a similar game)
