I'm not sure why I put the reprint before the original this time around... it's Amazing Spider-Man #2 and the reprint in Amazing Spider-Man King-Size Special #7. Obviously, a new cover was done for the main feature as well as the additional stories... interesting that the "A Guy Named Joe!" picture still looks like Ditko, eh?
Coloring can make all the difference in the world, can't it? Here's Sgt. Fury #16 and the reprint in Special Marvel Edition #14... i think the original cover has the better coloring.
Next, Daredevil #24 and the reprint in Marvel Adventure #3. At first glance, it doesn't look like any change was made, but for some reason, Daredevil was at least partly redrawn! That's a new head, and the right arm was either redrawn or cut and pasted with some additional art corrections!
Fantastic Four #65 vs. Marvel's Greatest Comics #48... Reduced slightly, and shifted down, but I don't see any other changes, aside from coloring (which was better on the original, IMHO).
Another "shift the image down" situation occurred when Tales to Astonish #82 was reprinted in Marvel Super-Heroes #37.
OK, this is more like it! When Avengers #52 was reprinted in Marvel Triple Action #44, the Grim Reaper figure was about all that was left from the original cover (well, plus a blurb), while everything else was redrawn or just plain added!
Aaaaaand... we're back to nothing significant being changed when Amazing Spider-Man #122 was reprinted in Marvel Tales #99. I guess someone realized it wasn't going to be improved upon!