But I have been a little curious lately, after having done countless mock drafts and a handful of actual drafts this season. So I listed the top 20 scorers from each position in my main league last year (espn ppr), and noted the dropoffs from 1-5, 1-10, 1-15, and 1-20, just to guage the depth of each position.
Also, some positions had a guy at the top of the pack that was way ahead of everyone else. So I also looked at the same dropoffs from the #2 scorers, as well.
QB:
-14 points (1-5), 68 (1-10), 103 (1-15), 136 (1-20)
-12 points (2-5), 66 (2-10), 101 (2-15), 134 (2-20)

RB:
-114 points (1-5), 152 (1-10), 183 (1-15), 196 (1-20)
-16 points (2-5), 54 (2-10), 85 (2-15), 98 (2-20)
WR:
-39 points (1-5), 70 (1-10), 89 (1-15), 111 (1-20)
-9 points (2-5), 40 (2-10), 59 (2-15), 81 (2-20)
TE:
-67 points (1-5), 91 (1-10), 117 (1-15), 131 (1-20)
-13 points (2-5), 37 (2-10), 63 (2-15), 77 (2-20)
Keep in mind, this was a point per reception league, so WRs (and TEs) had an advantage. But when compared to the top performers, the WR position had the lowest dropoff (2nd lowest when compared to the #2 performers).
So to me, it almost seems that it's more important to get a top RB and/or QB than it is to get a top WR in the first couple rounds of the draft. Thats odd for me to say, because I hardly ever take a QB early. But hey, I've never won any of my leagues (though in my three years of playing I have had some of the highest point scoring teams)! There just seems to be a distinct advantage to getting a top 5 QB, and really a dire need to get a top 10 QB.