It was for a long time, and during that time I was also exposed to and even came to like other RPGs, including skill-based and rules light systems. At first, I railed against a friend's comment that I was "stuck on a system" due to what I liked to play and GM, but I eventually saw his criticism as truth, as I tended to stick with games with D&D-like flavor. Dungeons & Dragons has fallen from its position as my favorite, in part from personal experience (although I must say I like 3.X more than any other iteration I've been exposed to), partly the "d20 only" attitude of some gamers, and my own personal distaste with certain role-playing precedents.