engineer: Believable design in a video game is.. laugable.
Besides, is it believable to be limited by "action po-
ints because I had to reload then fire my pipe rifle?
That's two different concepts there: setting and turn-based combat. The setting in Fallout is believable because it stays coherent from start to end and benefits greatly from it. That's why, among other things, you do not find items in inappropriate places, each of the locations has a theme that fits well with a post-apoc setting, most characters fit their locations and aren't too over-the-top — excluding joke characters, etc. You can see the difference with Fallout 2: that game had almost no coherence and did not have a believable setting. Not all games need it, certainly not a shooter like Painkiller, but it can add a lot to a game that lets you explore and interact with the environment, and that at the same time tries to tell a story.
On the issue of turned-based combat using action points, maybe you mixed the words "believable" and "realistic" up? Because turned-based may not be realistic but it doesn't impact the coherence of the setting. And if anything, it's a good indicator of your character's growth in power.