I don't think there is anything more iconic in the world of sci-fi than the fleet action.  Ironically, when you stop to think about it, there are remarkably few fleet actions on the silver screen.  Mind you, I am not talking about those fleeting scenes (pun intended) where you have a few ships shooting at each other for a few minutes, but a well-developed battle that is a focal point for a movie.  Using that criteria, I can only come up with the following:

1) Star Wars: Episode 4 (The assault on the Death Star)

2) Star Wars: Episode 6 (The assault on the Death Star...again)

3) Star Trek II: The Wrath of Khan (not exactly a "fleet" action, but a great space battle)

[Battlestar Galactica qualifies, but I left it off the list because that is a TV series]

That's really about it.  There are some lesser battles (the end of Serenity, for example), but most of these are just superficial firework displays at the end of a movie.

Isn't that amazing?  I think it shows you how poorly Hollywood understands sci-fi.