I stay away from Old Navy. I think they look like cheap crap, but that's just me.
Geerally, what jeans you prefer are dependant on what jeans fit you. If I want cheap (like..$35-40) jeans, I'll hit up Express Men. If I'm getting a nice pair that I'm going to keep for nights out or just want to splurge, there's nothing wring with Diesel
In my experience, I don't see too many people that try to make a fashion statement with old navy and are older than about 14.