jdrez: Agreed - it is polite and respectful to be appreciative.
It's not something worth being upset over, though. There are several other methods of gifting available, if you require a "thank you."
gameon: I dont know. I mean, if you spent loads of money on games and threw them in the ninja thread, and no-one thanked you, there would be no knowledge of where it went. Just an empty place that you threw your money away to....
If it's GOG games, you could always see who redeemed them.
Never is a waste. It's like you're saying "Hey, I gave a poor soul on the street 1 $ but there wasn't anyone passing by to see my good deed... what a waste".
I mean, it's between you and yourself in the end, but I do see your point.