Because I'm a geeky gamer girl
This was made by the same guy who did Dead Fantasy I and Dead Fantasy II, so you know it's good. Haloid is a crossover of Halo and Metroid (if you couldn't tell), so Master Chief vs. Samus Aran is a go.
X3
It totally gets fanservice-y at the end though, because... well, a fanboy made this. And Samus has a Zero Suit form. :P
EDIT...
Lies. It gets fanservice-y halfway through once Samus goes Zero Suit. But it's even more fanservice-y at the end. And after the credits, that is so much fanservice that I am quite embarrassed for all fanboys everywhere.
But the animation is very good!