Am I able to sell a Steam licensed game that I don't play anymore?

I have some games that has been registered to my steam account, but I am not playing anymore.

Can I sell off to someone else who wanted to play?

Solution 1:

No you cannot. This is part of the agreement you agreed on when you linked the game to your account. Therefor is also cannot be regarded unfair. As the comment suggests though there are a few new interesting developments, but so far no one really knows what they mean. Hopefully we will be able to force steam (and all other companies) to enable us to sell what we own, but for now, we cannot.

Evidence of this provided by Joseph Kendall: Steam Support Link

Solution 2:

In fact in Europe YES YOU CAN LEGALLY by court ruling, see link

http://www.webpronews.com/you-can-resell-your-steam-games-in-europe-2012-07