Racing Games : diversity

[ghettoglamour]

Sonic & All-Stars Racing Transformed -> Best kart game right now
The Dirt series
The Motorstorm series (especially Apocalypse, which is unique)
Blur aka Mario Kart with real cars and "realistic" physics.
Split Second
Shift series
Grid series
Driveclub

That's all I can think right now, but there is enough diversity!