I´ve owned Dark Souls for a couple of years now and always played for a bit, got stuck somehow or frustrated, and put it back on the shelf for a while.
I also have the tendency to delete old saves and start over, so I´ve been playing the Undead Burg section for at least 8 times already.
During each attempt at the game, I always learn something new, like how upgrading weapons works, how to get to certain parts of the games earlier, how to distribute stats etc.
I started a new Knight save a couple of days ago and then just for the hell of it started yet ANOTHER file as a sorcerer. Finding that smith hidden in the New Londo Ruins, making a magic weapon, farming for green titanite shards in Blighttown...
...I learn something new EVERY time I play the game. There´s always some way to make the run different. By now I should be burned out by attempting this game so many times, but it´s like I´m not just making progress in the game, but learning new stuff ABOUT the game.
And that feeling when I beat the bell gargoyles on my first attempt when those gave me so many problems back when I first played the game... It´s such a rush.
I don´t think I´ve ever had so much fun with the first few hours of a game. I´m actually enjoying it MORE than the more often I play it, not less. That´s the sign of a brilliant game right there. Feeling confident and knowing stuff about the game after being in the dark about many of the systems and secrets for so long is very satisfying.