For me, yes. Every year, I try to clean out most of the old games I have beaten and do not plan on playing again. Its pretty good, since it allows me to get older games I might not have gotten the chance to play (For example: Bought Call of Duty 3 and Hitman: Blood Money on ebay for $30.00 the other day).
Best thing I do is have a shelf for all my games, one for my "must keep" games, and one for the games I have not beaten yet, beaten and do not want to keep, or plan to sell. Usually, I will sell the games I no longer want every Spring, Summer, and Fall/Winter. Granted, there are a few exceptions, such as rebuying old games when they are cheaper (Bought Sonic the Hedgehog for the 360 on ebay for $20.00 since I sold it before beating it, and Zelda: Wind Waker and Master Quest for $30 since I lost the case to Wind Waker and still need to beat Master Quest).