Generaly, for me is better to take only concept and gameplay from old game and nothing more.
Pure 1:1 remake is pretty boring for me (except Ballerburg!!
There are few iOS game that have similar concept of old ST/Amiga games but they are improved in many ways.
E.g. I found Defender Of Thr Crown pretty borring and unactractive on iPhone but I can bet that new game, based on concept on DOC, would be great on iOS!