The wrong winner?

If you've already given him the game, it's a bit late...

Yes, you can always request a new winner if you give away a game collection or a GOTY version and the winner already has one game of the collection or the base game of the GOTY version.

Since you've already given the game away, there's nothing you can do now.

It's too late now. But in future, you can request a reroll if the winner already owns some of the games.

He might have gotten extra copies of the games he already had, so try to ask for those back.

Don't know if you did it, but next time, write in the description how many/which games people are allowed to own to enter the giveaway... :p (half of the pack, not more than one game, no game of the collection, ...)

Too late, but yes, you can :) Though it might help to specify in the description of the giveaway that you want someone who doesn't have any (or most) of the collection to win :)

Yes, if the winner already own a large part of a bundle it's a valid reason to request a re-roll.