Both shows contain extremely colourful scenes and have a Slice-Of-Life catered feel. The topic of aliens is also present in both in which, 'Tsuritama' has a main character who is an alien and 'Kono Danshi, Uchuujin to Tatakaemasu' has a main character who defeats aliens. The characters are also a similarity; the main casts being completely male. There are also some moments that take place in the main characters thoughts. Lastly, both shows contain very light Shounen Ai.
If you're looking for a a slice of life anime that features a cute little (and slightly clueless) alien boy who makes his home on earth, forges relationships and has one cute little boy dear to him, then this anime is perfect for you!
Bonus: Both anime have a very light Shounen Ai-ish feel to them.
Well they both have such colorful colors in the anime. Both involve fighting with something and also the idea of having support from friends or other sorts. Gives the same feeling and atmosphere. Though, Kono Danshi could be a little complex to understand. I really recommend both.
These two one-episode-only OVAs are very similar both in terms of art style, characters and story. They deal with themes like love and loneliness and share the same heart-warming feel, but at the same time they can get you on the verge of tears. They're very unique, so if you liked one of them you will enjoy the other one, too.
In both is a post-apocalyptic world brought about by some otherworldly threat. A teenage boy fights against this threat, but becomes increasingly more emotionally unstable. Communication with others is also a major theme in both. Kono Danshi is ultimately more optimistic then Evangelion though.
Art in both OVAs is similar. They also share the same feeling and in both a cell phone plays an importand role. Only difference is that Kono Danshi, Uchuujin to Tatakaemasu is labeled as (very light) shounen ai and Voices of a Distand Star is normal romance.