I like here. = I like this place.
I like it here = I like the (situation, circumstances, or general state of affairs) here.
Other examples of 'it' meaning (situation,circumstances, etc.)
How is it going?
How is it in China?
I like here.
This is a perfectly good English sentence.
Where would you like to have the party, here or in the park?
Ans. I prefer here.
here....noun...this place. Webster's 11th Collegiate Dictionary.
From the American Heritage Dictionary:
1. This place: "It would be difficult from here, with the certainty of armed gunmen inside, to bring him out alive" (Howard Kaplan).
2. The present time or state: We are living in the here and can only speculate about the hereafter.
and the Harper Collins Dictionary
1. this place
They leave here tonight.