Well that's just like your opinion, man :P

The fact that MegaBloks aren't Lego is why I don't buy the Halo stuff. I have tons of Lego I bought or my brother bought or that we inherited from older cousins and the like. Essentially it's ecosystem lock-in in a physical sense. There's also the fact that Legos are as Quirel pointed out, stiffer and less detailed but more versatile as a result (although I think Lego has been marching more towards the trend recently with specialized pieces.)

I assume there were a lot of factors working against Lego ever doing Halo toys, since Lego has Star Wars and it's both a bigger franchise and more explicitly kid-friendly, but my heart still wishes it came do be (I guess my wallet doesn't.)

Very fun little animations.