If you're looking for an arcade-style racing game, look no further than the Asphalt series by Gameloft. Similar to Need For Speed, you'll participate in a variety of race modes, picking up power-ups to give you an edge over the competition. The more races and crazy stunts you pull off, the more money you earn that can be put towards new cars. Feeling confident? You can challenge your friends in local multiplayer or take on the world in online races.
For the car enthusiasts that want a more serious racing experience, Real Racing by Firemint should be your first stop in the App Store. With 30 real world cars, stunning visuals, and a variety of tracks, Real Racing is the closest you'll get to Forza on the iPad.