I think this varies with the type of film. If it's a film with real fans and excitement is thick, a packed theater is amazing. OTOH, films where the audience isn't engaged, or dare I say invested, having a crowd can often just be annoying because of the chatter or people moving around.
I saw the first Star Wars movie on the day it opened in Boston, in an enormous, packed theater. I will never forget the roar that went up when Han Solo came out of the sun to save Luke.
I went to a pretty packed showing of Spiderman No Way Home... the reaction to Matt Murdock catching the brick was pretty awesome. It's definitely a better experience watching movies with fans of the movies themselves.
That said, it's also nice sometimes catching a mostly empty 2pm showing of something and getting the perfect seat without distractions... Especially considering if I turn up the volume to get the appropriate experience at home I get yelled at.
