It's the fun factor!
It's pretty easy to get the hang of it. The gameplay is great with the modes you can play in. The graphics are sharp and shiny, which it seems a lot of people like. The sound is pretty good, the music is one of my favorite game soundtracks. It's very addicting, I keep picking it up and playing again and again.The sense of speed that it gives you is great. I don't know of how I would change anything to make the game better.
A few races are kind of frustrating at the end of the career mode because they get hard, although it wasn't a big deal for me.
I think the way I would classify this game is "Great fun, go get it."