I badly want to start a Fuji appreciation club, its one of my favourite tracks albeit after much practice and use in GT5P.
I'm surprised people don't like Suzuka too...I'm wondering whether people just like lazy tracks like High Speed Ring which don't take too much effort to win? I can't really see why Suzuka isn't liked as it does pretty much everything a great race circuit needs to do. In my opinion, its the definition of a race circuit.
My least favourite tracks is SSR7. I'm pretty happy at all the rest of the tracks in the game, though Tokyo took a very long time to really enjoy..since 2001 in fact.
SSR7 doesn't really do the right things for me, it doesn't really give much high speed racing because of the turns, and it doesn't really give much high speed thrills because of the long straights. Its trying to be two things at once, when really it should be a full blown motorway perhaps with a more complex section thrown in and let the old Test Course deal with high speed stuff.
I'm happy with the Ovals as they are sufficiently different to each other and I can enjoy Oval racing and its particular style. I do sometimes tire of the Nurburgring, especially if I'm in the mood for some hotlapping, as the lap is too long. Same for Le Mans, I really have to be in the mood for some long distance racing, I don't really like testing or free running around those two. I wish they had updated Monaco or at least provided a more detailed 2001 version, i.e. with a more accurate track surface, bumps and all. But none of those I could call "least favourite" as I do still enjoy them all.
I'm currently loving Tsukuba for its simplicity when it comes to straight cut hotlapping and testing different cars. Its very handy for tuning cars to a set laptime. Its easier to run a consistent lap with fewer corners, but there is still enough to test different cars' abilities (except straight line speed..but thats something that doesn't need practical testing so much).
Oh and

@ the Cape Ring hate. If it wasn't for my new found love of Tsukuba, Cape Ring would be the ultimate test track! Even if you hate specific parts of the full layout, you can run the variations, but I personally love all of it. The only thing it lacks is some negative camber corners and perhaps some higher kerbs and it would test pretty much all aspects you could think of for racing any circuit! Again, I'm surprised people don't like it, as its a lot of fun in any car.