The trilogy as a whole is a masterpiece and has almost 15 years, Three giant movies made in just four years, with an overall budget of $281 million, 17 Oscars + another 428 awards wins. It was revolutionary*.
All things considered, I think the vast majority of the CGI hold up VERY well, 15 freaking years and still better than many 2017 movies with way bigger budgets (cough, cough, JL, Wonder Woman, Transformers, Beauty and the Beast, Spider-Man, etc).
*(Gollum from The Two Towers was what convinced James Cameron that movie special effects had finally advanced enough for him to make AVATAR)