I mustn't be feeling well, but Richard Teph is right again. The changed flashlight mechanic in the other maps is a matter of personal opinion (I don't like it, others do, we'll agree to disagree) but the whole point of the Hell map is that you arrive with no gear and no armour, and you need to do some serious exploring to pick up stuff. Having the flashlight destroys a lot of that.
They should add a "game+" mode after beating the game that turns off the flashlight completely. Some of the shock effects (lights out, door opens, room filled with baddies) that the original Dooms had, just don't work with a flashlight.
I don't like the fact that these changes were made to make the game easier.....you know what's what SKILL LEVELS are for! Not this extra-ammo, armor-flashlight, brighter-levels hand holding crap!
If newcomers to the game (or game series) want it easy, they should play the Recruit difficulty. Monsters do 30% less damage to you.
I noticed that there are areas in the BFG release where there are more enemies (at the same time and respawning after another) than in the pc original.
The additional ammo makes some sense when taking this into account.
Looks like they tried to make Doom3 a little more like the old Dooms gameplaywise.
As for the brightness: Turn down the settings to minimum and it looks the same as in 2004.