The whole "Sci-Fi Aliens are Unrealistic!" trope has been around for ages. It's not wrong, but there's a pretty compelling counterargument that you can draw from evolutionary biology. The short version is that a) there are certain things that have evolved repeatedly on Earth and show clear selective advantage and b) there are certain environments where general intelligence and the ability to manipulate tools in complex ways has less selective value than other things, like an aerodynamic or hydrodynamic shape. As a result, tool using intelligent Aliens that make it into a full on technological society like ours are likely to have a number of things in common (stereoscopic front facing eyes, complex manipulators not involved in locomotion etc.) and likely have come down a relatively limited number of evolutionary niches (probably not exclusively aquatic, probably can't fly, likely not exclusively herbivorous etc.). I'm not saying the first Aliens we meet are going to look exactly like us but with slightly different ears, but to my mind, a Vasudan is vastly more realistic than a Shivan.
I should get around to writing this all down some day. :P