Stu, I love where pro pool is at right now, and it looks like there will be more to come. Promoters are beginning to see the value in the game (streaming) and that bodes well for the future. I am also excited about the great young players who are challenging the old guard right now and Filler is certainly at the top of the list. (Kaci was last year and Shaw was the 9-Ball king for a couple of years as well). IMO there are still at least 10-15 players who are near equals, and all are capable of winning any major event. That list will probably grow as well in the near future.
Sadly, I have seen Jon Kucharo come from nowhere (Bettendorf, Iowa) to contend and beat the best players in the world by the age of 20. By age 22 he was washed up, a victim of his own success. Many years ago, there was a teenager named Mark Beilfuss from Michigan that beat all the great 14.1 players that came through playing exhibitions. At 17, he may have been the closest to Mizerak there was. He was out of pool before he hit 20. Michael Coltrain was another great young player sidelined just as he was entering his prime in his mid 20's. There have been others (Chan Witt) and the kid from California who died to young to fulfill their destiny.
Once Johnny Archer quit being a bridesmaid, he seemed to win everything, starting at age 21. Of course, his career continued throughout the 90's with his being named the player of the decade. He was still in his 20's in 1999-2000. So, we have seen other prodigies, but none of them won back to back majors against elite fields like Filler has done. IMO he should have won this one too, but had a lapse in the final match. It was definitely not his best performance.
Kucharo was not on this level. I saw him play many times when he was 20, as well. Yes, he had the best break at one point, but his competitive track record even then wasn't first tier. Neither Chan Whitt nor Mike Coltrian ever reached this level, either, although they had sad endings to very promising futures.
I don't think Kaci has ever been one of the world's ten best players. I'd put him around 15th.
I'm not familiar with Beilfuss, although his name is one I've heard before.
Appleton, who first found his top form in his early 30's by winning the 2008 WPA World 10-ball title, is similarly irrelevant. Not an early bloomer, and his best year, 2012, came at the age of 36. Yes, he has fallen off in his 40's, but his stay at or near the top lasted quite a while.
Immonen, who emerged at age 28 when he won the 2001 WPA World Championship was not as early a bloomer as Filler, but he's a good example of how hard it is to stay at the top. He regained his top form in 2009 in his mid-30's, but just like Appleton, he has fallen off in his 40's.
Shaw was an early bloomer, a world beater by age 25, but he wasn't really winning premier events until his late 20's. He was among the three best for a while, and he is still a monster. He played great in the World 10-ball Championship, even in his 10-8 loss to Filler in Stage 2. He remains a top five in the Fargo rankings, so if he's fallen, it hasn't been far.
The best comparison here is Archer, who was a spectacular player in his early twenties but first found his very top form when he won the 1992 World Championship at age 24 and went on to be player of the decade. By the way, he was 31 in 1999/2000.
I'm still looking hard for a player whose career began with such a bang as Filler's and I just can't find one, although Archer comes closest. Of course, Josh won't mass produce major titles consistently, and neither did most of the members of the BCA Hall of Fame, but his resume is awfully strong for such a young player, and he has a chance to be one of the greatest ever players.
Like you, though, I think pool is in an exciting place right now, and I'm more inclined to dwell on that than anything else. Let the good times roll. Who's the best? Now, it's Filler, but as you correctly point out, few stay on top for long, so let's just sit back and enjoy the show. Whatever happens, there should be plenty of drama with four majors a year on American soil (International 9-ball, WPA Players Championship, US Open 9-ball, World 10-ball). It's almost too good to be true, my friend.