I really tried to like it but it fell far, FAR too short of my expectations.
This game has so many flaws. First of all, the game hardly even gets racing right, the controls are bad (to me) and the racing can become frustrating. The story is also corny, and cheap. Never once did I feel involved and to this day I still haven't bothered going back and finishing it. It just sucks.
The biggest part this game tried to cash in on is the LBP-Wannabe Track/Mod/Kart creation. Let me just say, this is nowhere near as customizable as LBP. In track creation, Sure you can mold the terrain but everything else is just a pre-made prop. This makes it tough to create a decent track, which is why there are hardly any good tracks.
One thing I do like about this game is the mod creation. This is probably the only thing as, or even more customizable than LittleBigPlanet. The best part of the whole game is coming back every once and a while and seeing the top mods/karts.
But overall that's not really enough for it to be a good game for me. The fun wore off in less than a week, no joke. The last thing I did on Modnation Racers was trophy hunt with freinds shortly after getting the game.
This game appeals to different people. You really have to gamble on whether to get this game or not, and it all depends on your expectations.