I played AD&D in grade school and loved it. Then I played D&D in junior high, as I couldn't find the books for AD&D, complecated by the fact that my parents are -very- against D&D (and Magic, for theat matter). I got the books for myself in high school, and again in college, and just recently I repurchased the old skool AD&D 1st Edition books. God, I love those books. I haven't played with anybody since grade school because most roleplayers SUCK! My new Magic group has a lot of promising roleplayers in it, but as was mentioned, MTG lends itself to busier lifestyles, as RPGs take at least one 8 hour+ session a week to be involving. I can squeeze in 4 hours a week for roleplaying if I want, but it is a lot easier to play MTG for an hour a day, and play while my wife is in class or doing homework. Additionally, most people here recognize that you can "play" Magic (read the web and chat) while you're supposed to be working or doing work on a computer. So Magic is really helped by the Internet, while RPGs suffer from a more fragmented society brought on by instant information, at least for me.
So I still play both, although Palladium made a great system, and Rifts is an amazing campaign setting. Shadowrun (too many rules holes) and Battletech (1st Ed) both have a lot of great things going for them, but don't hold the simplicity and possibility of Palladium.
Erik