You're only saying it now? I've been saying it for years.
1. Mario Kart DS
2. Mario Kart: Double Dash
4. Mario Kart 7
3: Mario Kart Wii
5. Mario Kart 64
6. Super Mario Kart
7. Mario Kart: Super Circuit
8. Mario Kart 8 (obviously that's what all the drama has been about)
As much as I liked and played a lot of the SNES and 64 Mario Kart, I just don't like how the SNES game controls compared to the top 2 and the 64 has courses that run way too long. I mean, Rainbow Road is only done as 1 lap in MK8 because it is so freakin' long!
Double Dash is the last Mario Kart game I got a lot of multiplayer out of and love how that game handles with the GC controller. It started to change the formula up a bit and had some great strategy play with character specific items and swapping characters. If you dig into it, it's a very rewarding game and experience. Mario Kart DS was the beginning of my solo playing of Mario Kart and it delivers in a strong experience. It even has block fort in the battle arenas if you want some classic action. Smart move there. All Mario Kart games now copy what the DS did and it has a lot of top, killer courses for racing. Just a solid package. The only issue is the DS isn't as ergonomic to hold as a GC controller. Other than that, I can't say anything bad about it.
I rank Mario Kart 7 above Wii because I think it controls better but other than that, I consider the games pretty equal. So, for me, the high point of the series came in the GC to DS years and its just been stagnating since. I still like the games but it really doesn't seem like Nintendo is trying to much with the series or that they are unable to top what they did with the DS.