I found the xbox series somewhat enjoyable (nowhere near some of the older PC titles though) and a couple of people I know are fans of motorbike titles (take it or leave it here).
Will have to have a look at the wii version.
I use to absolutely love the ATV games for the PS2.
Multiplayer (I read in this one you can play up to 12 players in WiFi!) was sweet because you could race a friend, or just have a free ride and do tricks.
Going to check this out, doesn't look too bad...and the DS version of the game is also worth checking out