Additional thoughts!

A warrior, mage and rogue have been the three traditional role playing class archetypes since I have been playing games. In addition to that, the archer has managed to become an archetype of it's own:

Dungeons and Dragons, Ranger
World of Warcraft, Hunter
Legend of the Five Rings, Tsuruchi Bounty Hunter
Final Fantasy Tactics, Archer/Hunter
Aion, Ranger
Gauntlet, Valkyrie

The thief archetype is very traditional and is very unique and as the poster above, could be represented as a ninja even as ninja are very iconic as "thiefy."