I don't think anybody "should" have had the title. Hogan carried the title to national credibility and did the best business. Wrestling is all about putting asses in the seats, and Hogan did that best.
Now, who "could" have held the title and looked credible? Not many. Ted DiBiase is one. People keep saying Roddy Piper, but I don't think he could have held the title for any length of time and had people buy it, except for maybe at the very beginning of Hogan's run, but there was no way the title was coming off Hogan that soon. Rick Rude and Mr. Perfect are ridiculous suggestions. As much as I like Rude, and have a huge man-crush on Hennig, neither guy was ever a Main Event guy in the WWF. You have to at least have been on that level to be considered.
Andre the GIant was an interesting suggestion, but the problem is that he was just an attraction. Titles aren't typically put on giants for a reason. Macho Man Randy Savage had a title reign, and while business dropped, I think he was credible in his role, just not as popular as Hogan. Orndorff is in the same boat as Piper, as it would have had to happen at the beginning of Hogan's reign, and there's no way that was happening that fast.
Reviewing the general climate, I think that the only two guys who could have credibly pulled it off, and had any real chance of getting the belt were DiBiase and Savage. Savage got himself a lengthy reign, and DiBiase never quite got there, which is sad, but was the fright business move. Besides, it opened the door for his "Million Dollar Belt", which was an AWESOME addition to his gimmick.