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.)
Yes, you can use both examples the simple present and the present progressive.
They have different meanings but I guess you already know it.