For The Lion King the definitive version is the SNES/GEN release but there are also lower-quality ports of the game for NES GB and SMS. The SNES and Genesis versions are probably identical enough that they should be under the same entry, but the other ports are obviously quite different (SMS version has REALLY different levels). The same goes for Aladdin (GEN) having NES/GB/GBC ports and The Little Mermaid (NES) having a GB port, etc.

Should ports of the same game that are different enough to warrant separate speedrun categories have separate entries on speedrun.com or should they all be listed on the same page and simply have different category entries for each platform? I'm leaning towards the latter because I want to combine pages to simplify the games list but I wanted to ask for a consensus before I delete anything.

This is my personal opinion and recommendation. It will vary somewhat between games and from community to community.

In general I think data within a game should be comparable along some metric. If the ports don't have the same levels for the most part, they should probably generally be a different game. If we can't make any rough comparison between the two times due to a lot of difference in gameplay, this should probably also generally be a different game.

Most games combined under one game title have small and measurable differences. Examples may include lag differences, text differences, and possibly some glitch differences, among other things.

For example, Donkey Kong Country and Donkey Kong Land are not really comparable. I'm not sure how these thoughts apply to The Little Mermaid, but if some ports are that different, I'd highly recommend putting it under a different game.

Data within a game should have some relative use in comparing times in my opinion.