Both are huge. Sony has sold more Gran Turismo games than Halo in a complete lifetime.
However Microsoft has sold more Halo than Gran Turismo this generation. This generation Halo averaged 6m a year in 6 years. GT averaged 3m in 5 years.
I wouldn't say one or the other is bigger as both are huge. Lifetime I'd say GT but this generation goes to Halo with Halo selling 40m to GT's 17m.







