Did it, though? Do people really want to play as gollum? I think it only did as “well” as it did because of how hilariously bad it was, but who the heck ever said “I kinda want to play as one of the most pathetic villains ever created?”
Stealth games are a popular genre and I personally find the character of Gollum to be quite compelling and I think it could have been done well, but it obviously wasn’t.
I do a pretty accurate Gollum impression and have entertained friends with it at great length and sometimes to their annoyance so maybe I relate to the character more than is usual but I can’t be the only one.
I’m not a Lord of the Rings fan(in fact I’ve only seen the 1st movie) but I can’t imagine that their is much actual coherent plot in a game about a side character.
There is so much more that most people are not aware of that it isn’t so hard. This was based on the Unfinished Tales. Despite being a side character, Gollem has an interesting story arc and he is important leading up to the events that made it into the films. The dual personality thing is also somewhat unique, he isn’t completely evil.
As a story, I think it would have been better received closer to when the films were released, when the character was more popular and more normal people might have been interested (bonus, expectations for video game quality were lower 2003).