There are many points to why doom is much better than halo.
In this point I will bring up the multiplayer
In halo, it goes like this...
Whoever has the better weapon in the fight wins, if they both have the same weapon, it's whoever shoots first, I know this because the characters move so slow it's impossible to miss.
In doom on the other hand...
The game only has 8 (9 in doom 2) weapons, and that's all that's needed, because in shooters nowadays, there are a lot of weapons that are never used due to another weapon being much better for the job.
Also the game is based on pure skill with three things you have to be good at to have a chance to win...
Tactics. *Where to engage your opponet, what weapon to use in the area.*
Movement. *Ability to dodge enemy shots. Since you can actually move faster than half a mile per hour.*
Aim. *Duh.*
Many new people complain about stuff like the BFG being too strong, shooting rockets down hallways constantly is cheap, but any good player can easily avoid any of those things.
And in order to even hit a good player, you have to outsmart him/her, taking shots carefully to draw your enemy into a corner with the plasma rifle, aiming your rockets carfully so your opponet dodges your other rocket right into it.
Besides, nothing takes more skill than a good old fasioned super shotgun duel.