Where the heck do I say it's impossible to make a good film in "that" genre?!? Why do you have to assume someone backing up a movie you don't like are "excusing" the film? Anyway, we defer on the genre; for me, Titanic was not a romance with the setting being on the Titanic, it was a story of the Titanic with a fictional romantic subplot. IE: for me, the ship Titanic was the star of the movie, not Leo or Kate.
In no way am I saying success = a great movie but I'm willing to admit although I might think a movie is crap, it doesn't make it a bad movie and when I see a movie makes 1.8 billion, I'll concede my taste isn't above others, it's obviously entertaining in some ways to many, so I'll give it its due, just not my "type".
I like most movies, I appreciate popcorn movies, classics, adventure, sci-fi, whatever. Sometimes I like movies that entertain my senses, not just my brain; and sometimes I like my mind entertained, not my eyes/ears. Titanic fit 2/3'rds senses and 1/3's brain entertainment for me (the recreation of the era/ship triggers some brain action
). Not all movies are created with the same end result in mind.
That's a fine list of movies you have there shmokes, though I wouldn't classify Forest Gump as a romance. On second thought, it IS kind of hard to classify that one.