A question for those who study the NFL draft

Like any sport, it seems difficult at times to take a player's college football career and try to predict how he will do in the NFL.

On that note, I was wondering if some positions in football provide a higher level of predictability?

Assuming that a player in question played against enough quality competition in the NCAA to evaluate him fairly, what positions fit under the following three categories:

I guess I'm looking for anecdotal responses, but anything quantitative would be good too.

My uneducated guess would be the following:

1. Highest predictability - Lineman and RBs (great NCAA lineman and RBs have a high chance to make it in the NFL, others generally won't)

2. Least predictablity - Linebackers/DBs/WRs/QBs (some greats make it, but many NCAA players who were stars end up to be busts in the NFL.)

3. Out of nowhere - (which positions in the NFL have the most players who were not super-stars in College?

Any thoughts.