MX Unleashed is possibly the ultimate MX game
The good: Wide range of gear, bikes and pro riders, really good tracks with a wide range of difficult or easy tracks, plenty of different jumps.
This game definately deserves the instant classic, highly addictive and the solid awards.
The bad: You can change from a custom rider to a pro rider during the season, You can't go against pros, iffy handling
If you didn't like this game you could try:
MX vs ATV Unleashed (It's just as good overall)
I rate this game 8.6 out of 10 (Great)