You can turn retweets off for the people you follow. I follow maybe 100 people who post regularly but only allow retweets from a handful of them. Since I've done so, the quality of my feed has improved dramatically. Usually, when I follow a new person I leave retweets on initially but turn them off after two or three retweets because I'm only interested in what they say originally.

Incidentally, the iOS Twitter client also shows tweets in your feed which your followers liked. And you can't turn that off. I don't understand that feature at all and it made me switch to a third-party client.