When you use 'feels' in this way. This is known as a mental state verb. Other common mental state verbs are: 

> now, think, learn, understand, perceive, guess, recognize, notice,
> want, wish, hope, decide, expect, remember, forget, imagine, and
> believe.

Mental state verbs have propositional meanings. So they are referring to the fact the person using the verb is undergoing a mental process / experience. So you can use feel with any mental state you can experience, such as interested, or you can feel something is interesting, (in the present continuous tense you speak of) meaning it is a mental state you are experiencing now. 

To use feels instead of feel though, I believe it would only make sense like this: - 

> X feels Y is interesting

Where you are referring to the object of interest. 

You can read more about mental state verbs [here][1]


  [1]: http://grammar.about.com/od/mo/g/Mental-state-Verb.htm