I keep every game I love installed, as I'll usually play it again sometime. I rarely uninstall games that I merely enjoyed as my save file, and all my progress would be lost. I only uninstall games that I'll never play again and don't care about the save files for, but I usually prefer buying a portable hard-drive to provide the extra space I need (otherwise I wouldn't uninstall the game, unless I really disliked it, then I'd uninstall it instantly) instead.