I have both. Cro-mag's graphics are good, but frame rate is jerky, particularly with SFX and/or music on. Hard to get used to though.
Moto Racer is enjoyable - nice controls, just the right sensitivity, again a bit of slow-down, but generally good. Monotonous though, as you don't even race against people! You just ride around.
Both games don't allow you to race against other "humans", AFAIK.