A good relationship is far superior. Being in a bad relationship is always a worse choice than being single, always. And people who hang around in bad relationships waiting for something better are pretty horrible people. You should end the bad relationship, for the good of both parties, not just slum around waiting for your next person. I think people who do that are afraid to be alone, and that's a pretty bad sign.
A good relationship, like Prost said though, is something everyone should strive for. It's unbelievable that feeling sometimes, and being single does get lonely in the long run.