You've heard stories about how great J.R. Richard was at his best, and they are all true. What the stories don't tell you is how thrilling it was to watch him on the mound on a good day. He was the scariest pitcher I've ever seen. He was 6'-8 ½", and his three-quarters side arm fastball sometimes made it to 100 mph. Imagine a right-handed Randy Johnson with 30 more pounds of muscle, and you'll get some idea of how terrifying he was.
I don't think he was a great pitcher—great in the sense of being the best in the league for a couple of seasons—and it's true that he had an advantage when pitching in the Astrodome, the best hitter's park in the game back then. But midway through the 1980 season, Sports Illustrated's William Nack called him "the best right-hander in baseball," and that was probably true.
By 1980, at the age of 30, he was certainly on the verge of greatness. From 1976-1979 he won 74 games, completing 62 of them and averaging 260 strikeouts per season. He had over 300 strikeouts in both 1978 and 1979. As he got older, he seemed to be getting better and smarter, with a change that startled some hitters. (Of course, when you consistently throw everything, including your slider, in the high 90s, a changeup is going to be even more devastating.)