Actually Methos was in hiding as a Watcher and most Immortals thought he was a myth.I always figured that if Methos was that old, why is anyone ever coming after him? He's obviously the most bad*ss swordsman that ever set foot on Earth! Well he might just hide really well, I don't know.
Eventually though we found out just how Evil he HAD been.
That is what was so great about that Series, the character development