Sci-Fi is just a setting
Sci-Fi is a setting - in general the more it is treated like this, and not an effects-laden crutch for poor script, dialogue and ideas, the better the film is.
The first Star Wars film (ep:IV) succeeded because it took commonly used story elements and a relatively standard plot line and set these elements using a Sci-Fi setting. The effects weren't cheap for their time, therefore they didn't detract from the plot. Likewise the effects weren't the focus of the film either.
The second film (ep:V, The Empire Strikes Back), continued more or less along the same lines and while there was greater emphasis on the technology and effects, they generally didn't feel like they were shoved in just because they could be, and a plot was fitted around them afterwards.
The third film (ep:VI, The Return of the Jedi), showed a bit of promise but on the marketing (merchandising) success of the previous two, piled in with merchandising features often to the detriment of the film. It still worked as it wasn't too grossly overdone, but it did detract from the film.
The recent films (ep:I, II & III) were built from working out what (and who) to merchandise, fitting special effects around them and then trying to shoe-horn any form of plot but only only if there was space available.
The "Star Trek" relaunch was very much similar, but more from the point of starting with pointless special effects, incompetent plots and then throwing in a few "popular" actors and topping it off with a few nods to the original to keep some "spirit" of the originals in there.
The entire concept of films and where they come from is often lost, for example Impossible Mission was all about a team of people working together, not one single "super character" (played by a famous actor) where it became a more effects driven copy of any James Bond film.