Or "Never Give Up, Never Surrender", as the crew of the NSEA Protector might say.
300 is an amazingly made movie. If nothing else it's an exercise in style that stretches the boundaries of the form. It's also stunningly violent, unashamedly grotesque and determinedly mythic in its style.
What it doesn't do is give you someone to care about. The Spartans are violent bastards, the Persians are twisted bastards and frankly you end up cheering for the Spartans purely because they're the home team, not because you'd actually like to have them round for tea.
If you can get past having to actually _like_ characters, you can admire their determination and idealism instead. And it's well worth seeing - much like Sin City was, because you've never seen anything quite like it before, and people will be ripping it off for the next five years.