I rewatched the films (theatrical) recently and while a lot does work, Wood and Mortensen were fairly underwhelming, Wood especially being limited and choppy in his range, and Pippin was particularly underdeveloped until TRotK. The middle of the first film felt pretty rushed and dependent on the effects while there wasn't much plot in the second. Gollum was pretty good but at times too cheaply comical and I didn't like how literal the division and interaction between his Good and Evil sides were (although I realize it's hard to do something subtler on film).
These were "problems" that always existed. What would make them not "hold up" now as opposed to then?