Minus the first one, which is fairly innocuous anyway, those are all either incredibly broad similarities (i.e, the weapons comment), or storytelling tropes that are far older than doom (i.e, having you be humanity's last hope). Also, for the aliens comment, I was just pointing out that Halo 2 went to great pains to show that they
aren't "hideous alien monsters", although I suppose we can ignore that since it was the sequel. Either way, it says nothing of how the game plays, for example, only that the story from as far back as you can zoom is similar.
Also, the "Earth is invaded" comment confused me, as Doom took place on Mars, and Halo took place on Halo (also on a ship in the first level, but still not Earth). I mean, the first few levels of Halo 2 and the entire first half of Halo 3 took place on Earth, but still.
Nothing really much Halo does differently than Doom, besides limit what you can carry and reward you with more health if you go and hide for a while.
ummm...correct me if I'm wrong, but aren't those pretty big differences? If nothing else, you're going to have to change your play style dramatically between the two.
Look, feel free to ignore this as a "fanboi rant", I'm not trying to tell you how to feel, and if Halo's not for you, it's not for you, simple as. It's just that your post seemed like a gross over simplification to me.