I've looked at passenger manifests, using the Morse gold form search of Ellis Island records,http://stevemorse.org/ellis2/ellisgold.html
...but have been unable to find the arrival of Janos, your grandfather.
Have you done any searching of passenger manifests, for example for the other MELAGAs/MELEGAs shown on the same 1930 census with your father & grandfather? Zlatica has listed a few possibilities, and there are numerous others. There are also addition surnames from the same (or nearby) village, going TO Isaco,MO(and nearby towns) in different years., all potential clues.