Air,Air & More Air, followed by muck, mud, beach sand, off-roads, trails, jumps---all amongst breathtaking scenery!
In terms of the various tracks and course layout, I don't think these guys could have done a better job. Its simply a masterwork of creative and imaginative genius in terms of putting the various environmental elements together so flawlessly and with brilliant combinations that never leave you bored, and keep inspiring you to see and explore more.
For vehicles, they really nailed the different capabilities of each vehicle type, and did an especially great job on making each course feel totally different, depending on which vehicle type you choose. It literally makes each track and course feel different, depending on the vehicle you are driving, making for nearly infinite gameplay possibilities. Also, the tracks and courses have lots of different "Y"s in the road, side tracks, nearly secret trails, etc., and each of these tends to more or less favor certain or particular vehicle types, which adds a lot of strategy options and a bit of exploratory homework and diligence, prior to going "all-out", in order to optimize a given track for being able to achieve your best times or other goals.
The only reason I can't give this game a full "10" is that I thought the options for driver skins were pretty weak. Given the environment of the island, with cold spots, hot spots, beach scenes, mountain scapes and jungle areas, their should be a practically infinite selection of clothing and gear options for the drivers. Sadly, they are pretty sparse and furthermore, just plain lame. They are drab and practically all the same. Also, the vehicle skins are pretty good, but there should have been more generosity of vehicle skins and designs, even though the classes, functionality and performance of the vehicles is probably perfect.