Obviously, if you are not a big fan of the OSR, this is probably an easier question to answer. For the purpose of this question, I'm going to define OSR and OD&D, it's immediate offspring, their derivatives and clones.
What is your favorite Non-OSR type RPG and why?
For me, the answer would be probably have to be
Savage Worlds. It's a pretty flexible system that can cover most any genre. It played much better than I expected (when I playtested for the guys at White Haired Man) and I'd gladly play it again. Might even consider running it down the line.
For a less flexible system, I'd say Warhammer 40k: Dark Heresy, but I'm not sure if it's because of the system itself or if it's because it's the first game I played when I returned to gaming.
So, give me your answers if you would. I'd like to learn about (and maybe learn to play) some of the other RPGs out there.