I actually only started about a year ago. I've been trying to recall all those I've seen, and can only remember 7 series, all of which are fairly mainstream, I think. There's none I've seen I don't have any at least semi-major gripes with, so the lame answer is I thought Neon Genesis Evangelion, Death Note and Madoka Magica were mostly alright (maybe you hate them, I don't know).
All my avatars are from a comedy series I love-hate. I'm kinda embarrased by it, I'll pm you the name.
What's your favourites?