I had the experience of reading Sword of Shannara as my very first fantasy book ever! My dad picked it up for me at a comic book store when I was about 12. LOVED IT!
But again, I was 12. I went on over the years to read Elfstones, Wishsong, the Scions series, and First King. This last was toward the end of high school about seven years ago. I havn't picked up any of the newest books.
Reason being: I think I grew out of them. By then, I'd read some older-themed stories that weren't so "cookie-cutter" fantasy. Still, as my intro to the genre, I couldn't imagine a better start. (Looking back, I think I was much too young for Tolkien at that point...too slow)
I'd highly recommend the series to people with short attention spans or who don't read many books to begin with. If you're trying to get someone else into fantasy, Brooks does a good job of keeping the early Shannara stories simple (if predictable) and telling a good fantasy tale.