The "we should have takens"

[SirClintonPortis]

I don't follow the stuff leading up to the draft closely, but every year, we take propsects people aren't familiar with and some fans respond in a burst of passion about we should have taken player X with the pick instead.

Now, I am a bit curious about these Players Xs that we should have taken and whether we should have taken the Player Xs over the players we actually took.

Now, I can recall Kerrigan(Cameron Jordan?) and Trent(Okung) getting that treatment for sure, but my memory is shaky on the other players, so I could use some help about this here.