So I rewatched the first episode of Azumanga Daioh english dub for a personal project the other day, and I can't believe my younger self stood this! The voices were annoying and nasal, and the characters used all sorts of weird expressions that didn't sound at all like natural speech. It did have a cheesy sort of charm to it though. But you know that saying, that "once you go black you never go back"? Well, somebody should make a rhyming saying to the same effect about watching subbed.
It's not the original.
If it makes you feel better, japanese voice acting for most anime doesn't sound that natural either; it's usually full of animeisms (it's the best word I could think of), exaggerated reactions and the like, for comedic or dramatic purposes. Dubbing makes it more noticeable because
Once you go sub, dubs you will snub
Once you go sub, to dubs you can't rub