elendiel7: I don't understand why Lydia would be chosen. She has no character development, and she lacks any back story. Her dialog options consist of just ordering her around, looking into her inventory and asking what a housecarl is.
Fenixp: Well, TES games are a lot about building your own story. I feel it's not necessarily about personality of Lydia but about what do you get trough with her. Doesn't mean she wouldn't be way better if she actually had some bloody personality :D I guess that's why I really like the vampire girl from Dawnguard
Some of the companions in Skyrim have a bit of personality, Serana and Jenassa (despite being one of the first companions you may find, and her fairly low level cap, Jenassa has a LOT of random dialogue) come to mind, the housecarls tend to have none though, which is a real shame. If you want a companion with plenty of personality who also happens to be useful, Dremora Lords are the way to go.