It's between Richmond, Berkeley or Vallejo. Berkeley's easily been the most influential in the last 5 years (TYBG) but Vallejo was a lot more influential 10 years ago. As far as the rappers go, Richmond has bred some pretty good rappers in the last 10 years (Nio, Erk, Su, Hongry, etc.) and unlike Vallejo they're not all cut from the same Thizz cloth. The only recent Vallejo rapper I can think of that isn't on that hype is Moe Green... Cousin Fik and the rest of the new Vallejo camp are dope but their style sounds a little outdated IMO.
If you stretch it out over more than ten years though then its Vallejo hands down.