Angels & Demons vs. Star Trek
For the purposes of this comparison I am going to look at peak traffic to the movie website(s) and at opening weekend box office.

Star Trek's opening weekend is the clear winner with almost 40% more box office. But is the same true if you look at peak traffic to the website?

Yes. Star Trek (startrekmovie.com) clearly received more daily peak pageviews than Angels & Demons (angelsanddemons.com). The peak day for traffic to movie sites is typically Friday of the opening weekend, as it was in both of these cases.
OK, that was fun, but let's take another recent set of movies and see if the theory holds up.
17 Again vs. Monsters vs. Aliens

Clear winner in box office dollars is Monsters vs. Aliens. What about the movie websites?

The theory holds up. If a movie website gets more traffic it is going to rake in more at the box office. I'll keep my eyes open for an exception to this rule. Night at the Museum is coming out this weekend and judging from its website traffic it will have a great opening weekend... you heard it here first.