There have been ten Trek movies, and I'd say that two of them are accessible to mainstream audiences
I know exactly which two movies he's talking about
: The Wrath of Khan, and The Voyage Home. In the former, a new director and staff were chosen to remake Star Trek (ironic, huh?), and in the latter, they didn't take themselves so seriously and just make a fun movie.
Seems like two recipes for success to me, and J.J. seems to be doing to former (and perhaps will do the latter in the sequels). So I'm confident that everything's going to be just fine.