I'm trying to figure out how to write characters that are not human and at the same time make them interesting/appealing to people so they don't sound empty or boring. I like the realistic approach to aliens, in all likelihood, they won't look anything like us and probably won't have the emotional spectrum that we have or perhaps have no emotions at all. I absolutely despise the Star Trek/Star Wars approach to aliens, make them all humanoid with different skin colors or horns added to their bodies. It's huge problem when it comes to writing because people like to have emotions they can relate to, characters need to have emotions so then there is conflict, romance or a brotherhood of some sort between them. But I just want to avoid the typical trope of having characters with detailed backstories being humans.
I challenge you to include an species of translucent cell-looking blobs who speak telepathically, and make one of them a recurrent character. Also, they reproduce by splicing their nuclei in what could be described as a gory exchange of body parts that results in a new individual with a fully developed mind. Then try to figure out how a society of such beings would look like, and how they would interact with humans. Wierd, right? That's why humanoids are the go-to shape.
You can do whatever you want, but I think it's important to keep in mind that your audience/readership is going to be completely made up of humans. If humans can't see something they can relate to when it comes to your story, it probably won't be as successful as stories where readers can find some common ground with your characters regardless of where they come from and how un-human you make them.
Star Wars did have some diversity: Hutts and various assorted non-human-sized creatures pop up, but I agree that there are too many painted humans. Part of the question is how realistic do you want things? Because having every alien species happy in the same atmosphere with the same gravity isn't very realistic. That would make meeting some species very difficult. As to emotions, I suspect they'll be more similar than you expect. Fear, anger, love, lust - they are all useful for passing on your genes, and it's not a surprise that we see them in numerous Terran species. An emotionless species would have no incentive to mate or even eat, so I don't believe that it could evolve.