What I mean is that it never seems that enemies respawn, like the powder gangers never come back, it seems that once you clear a place out they never return. I enjoy Skyrim (Only comparing for logical reasons) because I know that if I get a sweet new sword or I'm bored and just want to kill stuff I can go to a cave or dungeon or an area and always (unless a bug chooses to intervene) find people there to kill.

And this issue is in Fallout 3 as well, I loved the first time I killed the enemies in the "Super-Duper Mart" but they never returned and that really svcked because their base was all set up and no one uses it after

So any idea why they don't respawn?

and no I can't mod it due to being on the PS3, my computers a potato so it can't run either Fallout...

Many enemies respawn. Which Powder Gangers are you talking about?

Most enemies in outdoor locations in Fallout 3 respawn after a certain number of game days have passed. Same in New Vegas, though there may not have been quite as many. Interiors, though, typically don't respawn.

the ones at their prison, and the ones outside of it... and the ones by the road... and well all of them I guess, I havn't seen them in so long, I miss them and shooting the dinomite before it leaves their hand.

Most enemies respawn, although for many, disintegrating or turning them into a pile of goo will prevent them from respawning in the future.

You have to leave the area for 3 full days though, if you return too soon the timer resets