Can I say 'I still wait for you'? Or 'I'm still waiting for you' is the only right form? Thank you.
Yes and no.
Let's say I'm waiting for a ride, and the person who was supposed to pick me up is late. If I called that person on my cell phone, I would say,
I'm still waiting for you.
I still wait for you.
However, that doesn't mean "I still wait for you" would be incorrect or inappropriate in all contexts. It could be used somewhat poetically – for example, in the closing of a love letter between distant lovers. As a matter of fact, the words "I still wait for you" are found in the lyrics of many songs, like this one:
Sometimes I think that my train done gone
The way all old things must do
Yet I still wait for its return
Just like I still wait for you
And I still hear that old whippoorwill
I've seen the ghost of a midnight train
And I still love to walk alone
Down by the old Union Station in the rain
(Always Loving You, written by Steve Young, recorded by Hank Williams, Jr.)