I didn't really have a reason to make more characters. I didn't feel like doing the same things over again, so I just did everything with one character.
-Got all my skills to Master
-Completed all factions
-Did all the quests I could find
I never really wanted to create a new character, because I could do everything with one character. I could be a heavy armor fighter, a sneaky theif, or a badass mage. Sure, certain skills were a little low compared to others, but I still didn't see the point of making a new character. I could do all the factions, quests, everything. The only reason I would every start a new character, would be to change my race and birthsign, which I never felt the need to.
I just hope they limit this in Skyrim. Kind of how you were only able to join one house in MW, so I would have a reason to make new characters.