If the game is just the same as it was on the other calc, then unless the original author wrote it, then it shouldn't be eligible. The reason we introduced the nomination system is because many people didn't want us deciding what programs got voted on. In response, we decided to put it completely the users' hands. That is, you can choose any program to get nominated. If you want these limitations, your nominations should reflect it.
Ported programs show no skill.
Maybe some ports are easy. Some are not. Games such as The Quest III for TI-86, which I ported, required quite a long time to port and in fact the 86 version is much different than the 85 version. And even if it hadn't been hard to port, it still would have taken quite a while and definitely some skill. Now I'm not saying that porting programs doesn't take any skill, it might depending on the program.