For me, it would be, no more fanservice and ordinary highschool MC that becomes OP in the next few episodes. I'd rather have Death Note like anime series instead.
As much as I don't like death note I agree with that :P
I am completely sick of fanservice and badly done tsundere.
I like sci-fi but not mecha, so Steins;Gate was great for me. Something really confusing time-travel wise would be nice.
I don't mind OP characters, or characters becoming OP really quickly, but it has to be justified and feel right, not just because of "plot". there a lot of that lately.
I am also partial to the stuck-in-a-game-world genre, but again it has to be balanced otherwise suddenly everyone is OP because of "plot". Also nothing feels awesome because its in a game. Log Horizon sort of balanced that a bit because it was a game, but also wasn't, kind of feel.
Basically an anime with actual story would be nice instead of cookie cutter stamped harem animes.
Done well, fanservice, tsundere, even harem isn't bad, but lately everyone is copying everyone else and theres no originality in story or personality.