Dark souls is a difficult game, yes, but the way people talk about it makes it sounds like the game is practically impossible to play. It’s not necessarily about how much skill you have, but how quickly you learn from your mistakes. You will eventually figure out how to defeat a monster or a boss. But sometimes it may take you a few hundred (An exaggeration) deaths before you get it done.
You say you’re willing to do a little reading? While you may not need to do much reading on how to take down certain monsters -and I suggest figuring it out for yourself because it’s more fun – you will definitely need a walk-through handy to tell you where to go and when. The game does practically nothing to tell you where to start or go next.

Skyrim can be very aimless. This is partly the reason I don’t play the game any more – And because all the mods require DLC I don’t have. You need to use your imagination to try and decide what to do next if you’re not following the main story-line.
I found that exploration was my main push after completing the story. But after I found and did everything, there is practically no reason to keep playing. That said, I did get a good 100+ hours out of the game.
If you do play Skyrim, take your time to do side quests when you get them and craft better armour, etc. don’t try and get the main story out of the way immediately.

Fallout 3 is my favorite game of all time. Even though it’s clunky and sometimes a little broken (I generally found myself ignoring and ‘quirks’ and just enjoying the game.) it has an a amazing atmosphere and it’s just a whole lot of fun.
The combat is very “meh” if you try to treat it like a shooter. Fallout’s combat works, and I never really found myself getting tired with it or annoyed by it. The combat isn’t brilliant, but it doesn’t take anything out of the came, in my opinion.
I’ve heard a lot of people say they don’t like the look of the game because it’s very dull and grey/brown. If Fallout was any more colourful, if would look very wrong. Trust me, you’ll find yourself wandering the wastelands with the radio playing for hours and hours.
Personally I found myself enjoying Fallout 3 a lot more than New Vegas. But New Vegas was the better game mechanically. I’d suggest Fallout 3 because it’s my favorite and because If you do start with New Vegas, you may find Fallout 3 awkward to play.