Has anyone mentioned Rifts? While not technically fantasy, it can scratch that itch. The pure insanity of the game can sometimes be fun in of itself. The real downfall of the whole game is that there is too much going on, and the game designers were not interested in balancing things with very opinionated views towards spellcasters, negative opinion.

If you are looking for lots of different classes many with very interesting powers and advancements I would suggest Rifts.