No clue how RC did but Motorstorm: Arctic Edge showed very impressive legs on the PSP.
http://www.vgchartz.com/game/32173/motorstorm-arctic-edge/Global/
Motorstorm Apoc sold pretty poorly and Artic Edge on PS2 was about the same as Apoc on PS3. I wonder if SONY would consider the series having a future as just a portable racer.
4 ≈ One