Ouch, that's a tough one...
I think complexity is the one attribute all the games hold in common. Also, I believe it is the greatest thing that ever held them back.
In all honesty though, it is the people you play with, which determines the quality and difficulty. Some people get hung-up on rolling the dice and micro-management of every damn aspect... While others actually focus on the actual "story creation", which was most games intention... Then others throw all that out the window, and just go free-for-all, only taking note of "rules". (Those are the real fun ones. However, you don't actually get much content, just a lot of laughs.)
For RPG's, I would say that the old D&D is the easiest to learn. The actual original box-set comes with an easy to follow, and play, adventure. They give you a real limited taste of the game. Something like only five or six character-classes, simplified rules, and limited supplies like weapons and food. It is a real "out in the rough", starting game. (It was enough to get a bunch of people hooked for more detail, so I still believe that is one of the best starting places.)
I think GURPS (Generic Universal Role Play System) would be the next step up. They use super-simplified rules which I think they setup as the "D-20" rules too. (D-20 is one 20-sided Dice, to play the whole game. As opposed to the classic set of dice, which was... D-20, D-12, D-10, D-8, D-6, D-4... Yea, a lot of dice. All for odds.)
You would have to pick just one format you like, to play any of the GURPS games.
For example, they have adventures and specific rules or expansions for things like this...
Star-wars systems
Worlds of magic
Worlds of psychics
Mid-evil (fantasy and reality)
Super-powers
Time-travelers
Prehistoric adventures
Ninjas
Robots
etc...
Pallalidium did the same thing, but using their own set of rules, which were also intended to be generic... However, it created the game "Rifts", as a generic "World" instead. The worlds attributes is what actually allows all those separate contents to exist in one place, at once. (As opposed to being Ninja's in old-world Japan, and being robots in the future, and being magical and psychic at the same time, all in present day.)
However, because of that odd world unity... The rules became a little more complex.
If complex didn't scare you... I would have said 40K Warhammer or Mech-Warriors. (They are both complex, where they need to be. However, there is not much content, just technical warfare battles to conquer and collect remains of those who fall.)
If you like card-games (For table-top stuff)... "Magic the gathering" and "Pokemon" are still real popular. Not my thing, but it still has a growing base of followers. Gets interesting with adults playing, as they tend to bet more. Apparently, this is where a lot of kids learn about betting, losses, and value. lol. I watched people bet entire collections against one another, money, and acts of personal humiliation... Was entertaining to watch, but I didn't have a clue how to tell who was winning or losing, unless you read their futile poker-faces.
Oh, also GURPS has a lot of "pocket-games"... Super condensed rules and adventures. Made to jump right into a game and start playing mini-adventures. (That is where I got my first games, "Car Wars", and "Vampires". They were fun for about a month, then I had to expand.
)
Any-one else feel free to chime-in, if you have other opinions or suggestions.
Funny stories would be appreciated too.
