I am not going to compare this to moto gp 08 or anything else. I am sure that there great.
I am more into cars than bikes, but just wanted to give it a try. I really enjoyed this more than i thought and found it addictive. The career is great and i found the sound effects, graphics, etc, excellent, including the rain on screen. What i did like, was the fact that when your racing, you have to be careful when overtaking as you'll go flying. With cars, you can clip and still be ok, but bike games make you more cautious.
I won't go out and buy a bike, but if anyone who likes racing games, whether, cars, etc, then this is worth buying for a challenge.