The great thing about old movies is that they feel like a time machine. I generally avoid watching the ones I have really good childhood memories of as there is quite a high chance that gets ruined. However, I do like to rewacth movies that get really high ratings but where I was too young to fully grasp it (Like Mulholland Drive / Donnie Darko just to name a couple).
Also many old classic films that I have yet to watch including some westerns like the good the bad and the ugly. There is so much out there to watch but so little time.
Enjoy the rewatchs!
RE: Revisiting movies: Starship Troopers and Waterworld