D&D is far from the best paper and pencil RPG ever?but it is a classic and it is good, the question of best?really comes down to best at what?
And even then it is hard to qualify.
My favorite system?the Hero System, you can do almost what ever you want with it, similar to Gurps?but in a better way. The only hassle is the GM has to work more to create his world?but once that is done ?it is fun.
But there are many bests, coming up with best overall?I can?t really. D&D 2nd ed with skills and powers/spells and magic/ I forgot the third?in the Planescape world?that was one of my favorite campaigns I ever played in and I liked everything about it including the system. But I can?t say it was the best.