This really depends on the artist and the listener. No matter how good it is, if the music doesn't speak to the person, then they won't like it. Some country really sucks (most of the "Nashville top 40" stuff like Carrie Underwood), and some is really good (Old Crow Medicine Show, Johnny Cash, Hank Williams, etc). Same with rock. Some is really good (Rolling Stones, Led Zeppelin, Nirvana, etc), and some is really bad (Nickleback). It is extremely hard to compare two entire genres of music. I personally enjoy both rock and country (there are even bands that mix the two. Uncle Tupelo is my favorite example). Where I live, Country music has a bad rep because you only hear the top 40 stuff, unless you actually go looking. I understand why some people don't enjoy one genre or another. Some music just isn't for some people, even if its not a crappy example of the genre. I personally do not enjoy rap/hip hop. Not because I think it is bad, it's just doesn't speak to me in the way Rock or Country does.
Bands listed in parentheses (...) are just my opinion and may not match every ones ideas of good music.