There were definitely some good moments of exploration in Fallout 3 with some cool locations you could stumble across. I liked the satellite dishes out in the wastes, many that were taken over by raiders; I like finding the Talon Company base; the Hubris Comics building; the overrun deathclaw village; the yao-gui caves, etc. The problem, I think, was that Fallout 3 was basically a dungeon crawler - one with more story than usual, granted, but just as Oblivion and Skyrim have been moving away from being about exploration, story, and quests and more towards killing stuff in caves and ruins, Fallout 3 was also extremely combat-centric and was totally littered with combat areas that had no real purpose other than being there. If that's your thing, then it's fun (and I explored the whole game pretty much top to bottom just for completion's sake), but that's never what Fallout was really about. It's also why New Vegas was such a great return to form for me. You still have the huge open world, but now the side locations are more for flavor and less the main attraction - and often they are flavorful, instead of "another sewer" or whatever. The game's focus is solely on story, quests and the world, and as such its exploration was a lot more satisfying... first time I came across the Brotherhood's base, it really felt like I had found something worthwhile, not just another bunch of super mutants to blast and loot.