I asked a similar question on Len Wein's run, but I recently reread Tom DeFalco's first Amazing Spider-Man run, so I'm curious what others think of it.
To explain the potential scores, as it's possible for one man's B to be another man's C...
An A+ is the highest score. It's meant to be pretty rare, an indication that this run is up there with the best of the medium (Frank Miller's Daredevil, Byrne/ Claremont X-Men, Neil Gaiman's Sandman, etc.)
An A is impressive, but not quite on that level. It would be among the best for the character.
A B indicates that the run is good but not great. The majority of the material is still worth rereading. In terms of quality, it's largely a success.
A C is pedestrian. It's neither good nor bad, and most of the material is probably not worth rereading.
A D is poor. It's a flat out failure. Most of the material isn't worth reading in the first place.
An F is worse.
DeFalco wrote Amazing Spider-Man #251-252 over Roger Stern's plots, before becoming the main writer. Due to fill-ins, he wrote Amazing Spider-Man #253-261, 263, 265, 268-277. Charles Vess wrote half of Amazing Spider-Man #277. He plotted Amazing Spider-Man #278, and wrote #279-283. Jim Owsley wrote over his plots for Amazing Spider-Man #284-285, so the credits are more difficult than average.
Frequent artists included Ron Frenz, Rick Leonardi and Brett Breeding.