I played a fair few Halo games in my gaming days (mostly Combat Evolved, Halo 3, ODST, and then Halo: Reach), but I have to be honest: I never really got into the story or background all that much for any of them. Maybe I should've, because the first two parts of Halo Legends proved very interesting, and made me appreciate the universe and backstory of this series a great deal more.
After that, the remaining five shorts are a bit of a mixed bag, as is to be expected from an anthology film, but I generally found more good here than bad. The most memorable of the bunch, beyond Origins, is probably the wacky very anime-esque episode following Spartan 1337. That one was actually pretty funny, though I can imagine it annoying series diehards, because it kind of makes fun of the Halo series in general.
Halo Legends fluctuated between the most and least seriously I've ever taken a piece of Halo media, and for that, I have to hold a weird amount of respect for it.