"There may be a lot of talented writers out there, but there will always be few who can spark revolutions."
There are so many English speaking writers today, compared to former time. Statically speaking, most of the best English language writers that ever existed should be alive today. If we made a list of the best English speaking writers up to now, statistically Shakespeare and Austin have a low chance of hitting the top ten on the list.
Is this a temporal bias towards early authors?
Sort of, but not really. Take rock music for example. When people tend to rank the greatest rock bands/musicians of all time, the top of the list is heavily weighted toward towards bands that got started in the 1950s and 1960s. When Rolling Stone compiled their 2011 list of the 100 greatest artists of all time, U2 at number 22 and Bruce Springsteen at number 23 were the highest-ranked artists whose careers began after 1970. In all, only 29 artists whose careers began after 1970 are represented. I wouldn't have made the same choices has I been in charge, but this list isn't appreciably different from most other lists that purport to do the same thing.
The reason these lists tend to be weighted heavily toward earlier eras is that quality isn't as big a factor as we tend to think. It's certainly a prerequisite (at least most of the time), but innovation and influence play a much larger role. To continue with the rock music comparison, The Beatles often top these lists, unless the compiler is a hopeless contrarian? Why? Because when the rose to prominence in the mid-'60s, they set the standard for what a great rock band is supposed to be. They put as much effort into albums as they did into singles, they wrote most of their own material, they were a self-contained unit that didn't rely on session musicians, and, of course, the music was great. And different; if you listen to to the top hits of 1963 and compare them to the top hits of 1965, it's clear that a seismic shift took place. By that point, it seemed like each album represented a drastic leap forward. While not quite as impactful, artists such as the Rolling Stones, The Who, and Bob Dylan had a similar ability for each album to spark some kind of revolution. Compare them to a more recent band like Wilco. I absolutely love Wilco, and they've made a number of incredible albums that I can recommend wholeheartedly and without reservation. But as good as something like Summerteeth is, I'd be kidding myself if I tried to argue that it had the same impact as Rubber Soul. Even Radiohead, the only band formed after 1990 that had the ability to consistently produce game-changing albums, still has to contend with the fact that the revolutions these albums produced were on a decidedly smaller scale. The most recent band to spark a large-scale revolution was Nirvana, but that was essentially a one-off; they would only release one regular studio album afterward, and the revolution itself fizzled out relatively quickly as the bands formed in its wake seemed more interested in milking the style than moving it forward.
You see something similar when people discuss the great works of literature. Shakespeare is considered number one because his work is ground-zero for English language literature. Every other entry in the literary canon marks a similar if necessarily smaller advance. I may be able to write a perfect hard-boiled detective novel, but no critic will ever rate it as high as the work of Hammet and Chandler.
So the problem for you is, what do you mean by "best". If you merely mean "as enjoyable to read as that which is widely considered the best" then I'd imagine that you are correct, and that there are a lot of great writers out there whom you've never heard of whose work you'd find great pleasure in. But suppose your favorite "great" writer is Edgar Allen Poe. If an author comes along who can write in Poe's style, but writes stories that you personally find more compelling than those of Poe, he may become your new favorite author. But no literary critic would consider him Poe's better; they'd see him more as a skilled craftsman than a true genius. Because for whatever it's worth, there's value in creating something original. If the work is derivative of Poe, then the quality would have to be far above that of Poe for the critic to regard him as Poe's equal. But this is practically impossible since originality isn't everything—Poe gets the acclaim he does because he work wasn't just original, it was also exceptionally good. There may be a lot of talented writers out there, but there will always be few who can spark revolutions.