Her was pretentious as fuck, imo.
How many people remembered Brokeback in 2007? The answer is "much less than in 2008". Good movie, but I would not say it's better than Titanic. Even if it was better, Titanic wouldn't really be considered overrated, because - well, because Brokeback was celebrated to the skies, especially after Ledger's passing. Probably more so than Titanic ever was.
I'm going to have to admit I haven't seen Before Midnight (because I assume you're talking about the before-trilogy by Linklater?). I really liked the first two movies, because they were interconnected. Taken as separate pieces, though, I can't help but think that they are very slow and dull. I mean the first movie is basically just two people striking up a conversation that would never happen in real life and continuing it throughout the movie.
ESSM is a beautiful film, and I would say that it is better than Titanic. But like I said before, for Titanic to be overrated, people would have to rate it above ESSM, which to my knowledge, they don't. (IMDB: 7.8 vs. 8.3, Meta: 75/100 vs. 89/100, RT: 88%/69% vs. 93%/94%)