When just looking at the core rules, gnomes are the best choice for wizards. They can have an effective build despite a low Str, gain the benefits of a small size (increased AC and a bonus to all attacks, especially effective with touch-attack spells), gain extra hit points, and can use magic to overcome any limitations from speed or weakness. They have a few innate magic abilities (bolstering their arcane options), and even without a human bonus feat get enough wizard fats to keep competitive. In fact, a gnome wizard able to make wondrous itesm is the best possible wizard build, since they can build whatever items they need (bag of holding, heward's haversack, boots of speed, etc).
Depending on the campaign, a gnome specialist may be a stronger choice, but in actual play I've never seen any racial option be better for wizards than gnome.