As I grew a bit older, though, I found that what I really liked was magic interpreted in new and interesting ways; the rarely-encountered "Art" of Tad Williams's  Memory, Sorrow, and Thorn trilogy helped me realize that magic could be even cooler when its use was more limited and its origins cloaked in shadow.  The more I read, though, the more obvious it became that the old fantasy axiom was indeed true: magic must have rules, it must have a cost.  There's nothing more boring than a bunch of showy magic with no apparent guiding principles or natural properties.  Which is one reason why Robert Jordan's Wheel of Time saga was so successful: no author, before or since, has imbued a system of magic with more comprehensive detail and logical insight than Jordan has (go ahead, prove me wrong, I dare you!). 

Lately, though, as Book Swede points out, fantasy authors are reining the magic in.  My almost instant love for A Song of Ice and Fire surprised me, since historically I've leaned toward books that dealt more with magic and the arcane than with out-and-out medieval politics and intrigue.  But that's the genius of this new generation of authors: they keep the magic in the background, so that it never gets boring, and their characters are all the more realistic and well-drawn because of it.  (George Martin's rare ability to kill off main characters just when you're really starting to like their chances also drew me in against my will, but that's fodder for another post.)