I tested them all, my opinion:

cubic world: simple as hell but well done, I spent some minutes with it and enjoyed, I like its simple graphics. it could be easily improved to have more types of enemies and different environments... should be a mobile game! (unfortunately not possible by 3dgs)

endless: the same concept with spaceships, but immediately crashing into an obstacle after start is not a good game experience. works, but the graphics style is outdated.

snombie: something very similar again, now against zombie snowmen. without an environment it gets boring very soon. it could be improved by a farer camera view and some walls or obstacles to move around and maybe to add a target location to reach... just a few simple things. the control is strange (imo it should be relative to character orientation), it is better in the above mentioned 2 projects.

panzer simulator: its overall appearance is a time travel to the 90-s, very simplistic, but playable. it was hard to shoot precisely, while enemy shoots fine, team color and minimap would help a lot to identify what is the target... with 1 day work it could be a good game. the wrs file means it was made with a pro edition, where a much better lighting and shadowmapping and terrain multitexturing is available, you could use trees, water (rivers, lakes) and rock and buildings in the environment (free stuff available).

painkiller: nice for the 1st look, but the animation and movement speeds are not in harmony, character movement and fight is very simple, the lift is really should not be there, stairs would be better, the environment could be much better with a little work, enemy AI is not really fine tuned, and after entering the big yard with more enemies it crashed here...

pixelit: maybe a practice project, but works.

project aum: good idea until the database is maintained, but unfortunately unfinished, imo today it is better to have similar things online. in this form I cannot really use.