Seleucus Nicator was the greatest of Alexander's successors. Went from powerless and exiled after the Second War of the Diadochi to the long and successful ruler of the vast majority of Alexander's empire, and came within an inch of adding reuniting all the empire except Egypt. Cunning general, cunning ruler. Actually understood that he ruled easterners in the east, and that in order to stay in power he needed to rule them.
Antigonus Monophthalmus is number two; ultimately he failed so it's hard to put him above Seleucus when Seleucus is the one that won. But Antigonus was such a ridiculously towering figure from 316-301, it's impossible for me to put anyone else close to him.
Ptolemy was too limited in his ambitions to top the list; that was probably a smart thing, but still, he gets penalized. Doesn't get points for the longevity of his dynasty.
If I was rating purely on generalship, Eumenes might get an argument from me. Antigonus or Seleucus might still beat him, but I'd have to consider Eumenes.
Who would you say of the group acts the most like Alexander?
Demetrius, hands down.