Fallout 3 was a great game. Fucking loved it, especially the bandits and the zombie radiation things whose names escape me (haven't played fallout in ages). I really liked the side missions too, like the one with the cannibal town and then you'd pick the lock of their shed and find human meat there, that was fucking sick. And the Combat, I like how the enemies scaled and the massive mutants. I'm not a graphics whore so I don't care if it isn't the single most realistic thing I've ever seen, but that being said, I hope they got a much better engine for this one.
I loved New Vegas too, but I lost the damn disk and never got to finish it, I was playing Hardcore all the way through, the feel of being in the west is just my cup of tea too (or cup of dark black coffee boiled up in a tin can on a campfire in the Mojave). Thing I liked most was the ability to create things at stations, I love love love that kind of ability and I hope to see its return in Fallout 4 and the companions options and how factions worked. I really have to get that game again.
As for FO4 itself, I'm glad Bethesda is taking another swing at it as we head into this new gen of gaming. I almost wish they'd take this whole other year to make it look and feel the best it can but I'm not sure I can wait that long.