MKW is good, and has some good new stuff, but it has really dumbed down the series.
Enough with the good stuff. Nintendo also seriously broke the game in a lot of places. To start, there were the "retro" tracks. Whether this was just a lack of will to make more new material, or a halfhearted attempt to hook series veterans, it didn't work. The older tracks, especially the NES tracks, were just monotonous when compared to the shiny new tracks. The second objection stems from the increase in drivers. Sure, the new tracks are big, but the older tracks simply weren't designed, and couldn't be modified enough, to make them hold 16 drivers well. The 16 drivers also led to the last, and probably BIGGEST concern with the game. It gets cheap. First, there's fewer advanced moves, notably, snaking. How can you hold an MKW tournament, with a lack of moves that some might not have mastered (this contradicts Nintendo's intentions in putting in 16 drivers, and online multiplayer)? Also, players that are back before say, position 7, get a massive boost in item quality. I understand that inexperienced players may need a bit of help getting started, but experienced ones hate it when someone in last place blasts them with a blue shell, the get hit by lightning, they get inked by a Blooper, and they get whammed by a red shell (true story) all right before reaching the finish line. Most of these items were thrown by people how get no profit from it.
MKW is a good game, but don't expect to be able to keep it interesting after mastering it.