Why do you think it is a better game? Provide reasons.
1. SSB has aged greatly among most other Nintendo titles. And that includes Mario Kart.
Example: If you check reviews and scores, you can see this is true.
2. It has loads more action than MK8. You can now have 8 people fighting at once with so much happening at one time.
Example 1: I was playing SSB yesterday with a bunch of students in my academy. We were having so much fun, many of us were yelling. Luckily it was after school. If you manage to play 8 players on the same system, you would know what I mean.
Example 2: Once someone has complete advantage and way ahead of the competition, it's over unless they really really screw up. It would be hard to regain control. With SSB, just watch all of the comebacks and you can see anything can happen. I've seen it with my own eyes.
3. It can never get stale no matter how long you're playing it. I found racing games to be boring after a period of time.
Example: I have played numerous racing games such as Need for Speed, and yes, even Mario Kart. I would play the game for a couple days then return it. It got real bland.
Side Note: I am not disrespecting Mario Kart or racing games in general.