You can always use some good mods for Fallout 3 to extend your playtime, but seeing as you have 200 hours, I expect it is very stale. I'm going to recommend Fallout: New Vegas anyway, and be sure to mod it up (and it's much more stable than FO3). Skyrim is a lot like FO3 in its open world expansiveness, since it's from the same developer.
Although S.T.A.L.K.E.R. is often said to be like Fallout, the games have a very different feel. S.T.A.L.K.E.R. isn't true open world (has loading screens) but more importantly, it doesn't have emphasis on open world exploration, side quests, or RPG elements. They're more focused on the story and main quest, which isn't much of a focus in FO3 or Skyrim.
Still, Shadow of Chernobyl and Call of Pripyat (especially with the right mods) will feel like Fallout 3 with the right mods in one way; they're both brutal and desperate. You can't just run around and dominate, you need to plan your course of action very carefully. I always end up deciding where I want to go and why, because you can't afford to waste ammo or get injured too badly. These are the best survival games, but they require mods to be this way (especially Fallout 3).
For those who are concerned: I use Win 7 Professional x64, and play Fallout 3 with DC Interiors, Mart's Mutant Mod, Simple Needs, NMC texture pack w/ bump maps, Weapon Retexture Project, Classic Fallout Weapons, Better Power Armor (and a re-skin for T-51b), and probably more mods I can't think of right now. My game hardly ever crashes.