Didn't you get all those keys from the developers, for free anyway? I think a GOG for any of those codes is more than enough.
You are right , but my GOG wishlist is growing in every week , and my gaming budget is empty .
edit : Speaking about free games . You forget about the trading histeria of Dota2 and CS:GO . Those are free beta keys . Also you forgot about the TF2 crap trading .
I hate beta key and item trading :), at least you're offering something legit but trading beta games and tf2 items for AAA games (or even for money) is just wicked imho.