I started out watching Taiwanese and Japanese dramas. However, once I tried South Korean dramas, they quickly became my fave. :)
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1) South Korea - Love-Love-Love - Not just the dramas but also the language (and culture - especially in historicals).
2) Japan - I've enjoyed most of the dramas I've seen, and I really like the language (and culture).
3) Taiwan - I really like the language (Taiwanese dialect Mandarin), but the dramas are much more of a miss than a hit for me. However, the handful of "hits" I've found have been fantastic and are some of my top-faves.
4) China - The language ("standard" Mandarin) is more difficult for me to pick up / understand (and enjoy), probably because I started out watching Taiwanese dramas. Also, I'm not a big fan of the dubbing. I find it extremely distracting when the voices sound disjointed (because of studio dubbing) and don't match the actor's lip movements. However, I'm finally starting to get more used to it and am enjoying most of the dramas I've seen so far.
5) Thailand - The language is very difficult for me to pick up / understand, and still sounds a bit strange to my ears. Also, I have to mentally prepare myself before watching most of those, because of the frequent rape.
6) Hong Kong - I've only watched a handful so far, mostly because I find the language (Cantonese) to be very jarring, and thus distracting. It's also extremely difficult for me to pick up / understand.