Mario Kart 7 has definitely improved the franchise, but it has also lost some of the beloved features.
Mario Kart 7 also lost some of the beloved features, such as variety of characters. Although you get to pick from the classic characters such as Mario, Peach, Luigi, and Yoshi they have added some characters that should not have been added. Such characters as Metal Mario and Wiggler do not belong on the track for which Metal Mario is hardly different than Mario(other than color) and Wiggler is way to big for a kart. Although some of the new characters are cool the way to unlock is somewhat too easy, you just have to beat a cup in 150cc Grand Prix to unlock one character(except for the Miis).
Maybe the characters are not so great, but the 3D effect and quality make up for the features it has lost. The quality is definitely great and unlike other 3ds games this one does not usually get blurry with the 3D effect. The road is better drawn and the stages are widely graphical. The quality is one amazing feature to the series that brings it up.
Another fun thing to do is to battle it out locally with other people. Racing with other people is way more fun than playing with just CPUs. Another fun thing about playing it with other people is that you can unlock stuff with other people. You can unlock them by getting coins or you can unlock characters if one person comes in first in 150cc Grand Prix.
Mario Kart 7 was a marvelous addition to the franchise, it involves skill and luck, it brings out the Mario Kart driver inside of you. It equally balances the items so everyone has a chance of coming in first place and even though you only get to race seven other drivers the game is still is as fun, if not greater, than other games in the series. If you liked Mario Kart predecessors then Mario Kart 7 is a must have to fully complete you and your series.