The quality varies greatly with these kinds of streams. There's really no way to make it better, all you can do is try to find a stream with better quality. ESPN channels are notoriously difficult to keep illegal streams for. So the streams change on a very frequent basis.
You can try some other popular streaming sites:
As has already been said. DO NOT install anything from any of those websites. They provide legit streams, but most of their ads/links/etc are all spyware/malware. The popups will lie and say you need this plugin or that update. Ignore it. I can't stress this enough.