I've always wanted to take a look at the pitchers considered #1's and research exactly where they came from. I never seem to find the time, so maybe someone with time on their hands could do this.
I have a feeling that they don't come from guys like Taillon. I would guess they are guys that were decent pitchers that found something extra during their development, like some extra mph or movement on the fastball, or a plus secondary pitch. Or maybe they are guys that just learn to be consistant. I wouldn't be surprised if some of them really struggled at one point and were considered #3 pitchers.
My point (that I can't back up with data) is that I don't beleive drafting a pitcher in the top 5 or 10 overall is the best way to obtain a #1.
People have a lot of different definitions of what a #1 pitcher is, but here are the top 15 pitchers based on WAR last year and where they came from:
Zack Greinke: 1st round out of high school (6th overall)
Justin Verlander: 1st round out of college (2nd overall)
Tim Lincecum: 1st round out of college (10th overall)
Roy Halladay: 1st round out of high school (17th overall)
Felix Hernandez: International Free Agency ($710,000 bonus)
Cliff Lee: 4th round out of college (105th overall)
Javier Vazquez: 5th round out of high school (140th overall)
Jon Lester: 2nd round out of high school (57th overall, $1 million bonus)
Dan Haren: 2nd round out of college (72nd overall)
CC Sabathia: 1st round out of high school (20th overall)
Adam Wainwright: 1st round out of high school (29th overall)
Ubaldo Jimenez: International Free Agency ($50,000 bonus)
Chris Carpenter: 1st round out of high school (15th overall)
Josh Johnson: 4th round out of high school (113th overall, $410,000 bonus)
Josh Beckett: 1st round out of high school (2nd overall)
They're mostly first rounders or guys like Lester who got the highest bonus of any second rounder and Felix who got a pretty big international bonus. 4 of them were top 10 picks. Greinke and especially Beckett probably got similar amounts of hype out of high school as Taillon, though a lot of other guys have gotten that same hype and failed. Most of the guys were projected as possible #1 and #2 starters at the time of their signing, although many of them weren't thought of that way until after getting a couple college seasons in. Your best bet for getting one of these guys is to take them in the first round, but there's also a very good chance they don't do anything for you.