Last year, Steam finally allowed you to hide games in your Steam library to help decrease clutter. Now, you can finally remove games you don't like completely.
It's a little convoluted to remove a game, but it is totally possible now. Just head to the Steam support screen (Help > Steam Support), select the game you don't want, then select "I want to permanently remove this game from my account." That should make it a bit easier to clear out the junk you never plan on playing ever again. Be aware though, when you delete a game, it's gone for good and you won't be able to download it again or play it anymore.