The worst:
-El Capitan - It's boring, bumpy, impossible to keep the wheels on the ground, and ugly.
Others I hate:
-Twin Ring Motegi (ALL of them) - They are the most boring, featureless tracks in the entire game. They have some difficult corners, but there's no fun, it's just endlessly grey and dull.
-Fuji Speedway 2005 - Another incredibly boring and featureless grey wasteland. There's so much grey that it's hard to figure out where the track is a lot of the time.
-Fuji Speedway (all others) - Boring and featureless
-Hong Kong - BORING!
-Special stage route 5 - BORING! I hate street courses.
-Suzuka (all of them) - The corners are all layed out in a goofy way that's challenging but not particularly fun
-Sarthe - You can only drive in straight lines for so long before you want to just fall asleep...
-Seoul - Boring street course
-New York - Boring street course again
-High Speed Ring - I don't like the corner layout plus it's quite dull
-I hate pretty much all the rally stages with the exception of the Italian street course which is very challenging, and the Paris tracks... don't know why I like those
Wow... after reading that, I'm pretty full of hate, lol. So, for some love, I love:
-Autumn Ring and Autumn Ring Mini - best two tracks in the game, I love the chicane section, and they are even better in reverse.

-Deep Forest - Beautiful and fun
-Trial Mountain - Beautiful and challenging, but in a fun way
-Nurburgring - What a challenge!
-Grand Valley - Beautiful and fun
-Laguna Seca - I've always loved that hairpin
-Tsukuba - I LOVE this track, it's so simple and fun to drive, yet somehow challenging as well