High five, Khush! (I was trying to type "^5" in the prior post, but I must have hit some key that made it post "^"!
Anyway, to better explain my picks (I was lazy at the time of writing the list):
Mario Kart DS - I really liked the tracks, the mission mode (especially), I loved many of the tracks (Delfino Square is my favorite from the game, along with Airship Fortress, Luigi's Mansion, and Bowser's Castle-- though I didn't care for Yoshi's track, the desert track, or the figure 8 circuit) and the online, penis emblems and all! Oh, and the implementation of regular retro tracks-- Super Circuit notwithstanding.
Mario Kart: Double Dash!! - I adore the soundtrack, I love the tracks (Mushroom Bridge, Baby Park, Bowser's Castle, Rainbow Road, Peach Beach, Daisy Cruiser, Dino Dino Jungle, etc.), I enjoyed the novelty of two racer karts, and I have a lot of nostalgia towards this game.
Mario Kart 7 - Features some really great tracks; the online was great; item balance was a little bit of a problem; I didn't like how kart pieces were unlocked randomly and with so much grinding;
Mario Kart Wii - Loved a great many of the tracks, loved how many characters there were and how varied they were, online was fun, but battle mode was nerfed, and the item balance was way too poor; oh, and I didn't like how I couldn't play the grand prix with my brother to unlock stuff like every console MK prior
Mario Kart: Super Circuit - I love the art direction of this game, watercolor/pastel-like; great amount of tracks; I'm not really big on the 2D Mario Karts, despite growing up on Super Mario Kart! Also, driving was a little slippery to me.
Mario Kart 64 - Loved, loved, LOVED this game growing up. Still contains my favorite soundtrack from the series (with Double Dash being second). Features my favorite Bowser's Castle track iteration. Battle mode was great. Some tracks were just "there," but I did enjoy the majority of them. My real problem with this game now is just how blatant the rubber-band AI is. It makes grand prix runs a chore.
Super Mario Kart - AI was cheap, driving was slippery, many tracks are just boring now to me (but that's obviously because of what's available now), but it's still a fun game. I'm looking forward to an eventual NA Virtual Console release.