Here's some analysis. I looked the Pro Bowl appearances of Wide Receivers and Guards in the 5 games this decade and the number those picks were each drafted at. For UDFA's, I assumed the number 260, since drafts are over in the 250's. For WR Josh Gordon of Cleveland, I assumed the #39 pick that Cleveland gave up in 2013 for picking Gordon in the supplemental draft. I counted someone whether they were originally picked or a substitution, regardless of whether or not they played in the game.
The average pick of a Pro Bowl WR was #69. The average pick of a Pro Bowl G was #90.
When broken down to number of appearances in each range, there were 48 appearances of WRs and 35 apperances by Gs in the 2010 Pro Bowls.
The Top 10 draft picks account for 15/48 Pro Bowl appearances at WR (31.25%). The same range accounts for 1/35 (2.86%) appearance at G (and that one should be considered a fluke, as it's Leonard Davis, who was originally drafted to play tackle.)
The rest of the 1st round (picks 11-32) accounts for 9/48 apperances at WR (18.75%) and 12/35 appearances at G (34.29%). It should be noted here that none of these guards were drafted above #17 (Steve Hutchinson and Mike Iupati) and Logan Mankins at #32 accounts for 5 appearances.
Rounds 2 and 3 (selections 33-97 by last year's standards) gives us 12/48 appearances at WR (25%) and 10/35 appearances at G (28.57%).
Rounds 4 and 5 (selections 98-168 by last year's standards) gives us 5/48 appearances at WR (10.42%), 4 of which are Brandon Marshall, and 7/35 (20%) appearances at G.
Rounds 6 and 7 (selections 169-254 by last year's standards) gives 1/48 appearance at WR (2.08%) and 0 appearances at G.
Undrafted picks made 6/48 appearances at WR (12.5%) and 5/35 appearances at G (14.29%)
Note that percentages may not add up exactly 100% due to rounding.
Now, what this tells me that obviously, as pointed out, the success rate does peter out the longer you go... but while the Pro Bowl WRs have their biggest representation in the Top 10, Gs have their big representation in the late 1st and 2nd/3rd rounds. Thus, to me, this data backs my assertion all along that great guards can and often are picked later than great wide receivers.
Now left tackles are a different story obviously. But this discussion did not involve left tackles, but only whether it was easier to find elite WRs or elite Gs outside the top 10.
But on the other hand, once someone makes a spreadsheet, the argument has probably gotten too silly to continue.
If you want to check my data, you can download the spreadsheet here:
https://dl.dropboxusercontent.com/u/31822673/WR vs G.xls