I understand that game development takes time and some money, but what is a game that is easy to make by ones self. I know that making games is not easy, but something that wouldn’t take 3 years by himself to make. If you have a game made by yourself feel free to post one down below. Thank you for your time.
Edit: Meaning not with other people completely solo.
pong
A little more advanced that that. 
Pong, I’m not sure you can make it (you might be surprised at how difficult it is to put together with score, and a start / end screen etc)… if you can do that then ask this question 
I already have. I just don’t know where the project is on my computer.
I already have done that. I need something I can sell to someone else.
First you said you wanted something easy, then you said you wanted something you could sell. Totally changes the
terms of your goal.
All easy classic game concepts you can think of have already been cloned many times and done better than you can or
should try to for an “easy to finish alone” project, which limits the marketability of your version.
So, make something simple that is your own original idea that no one has seen before, and make sure it is fun, and
it will sell. That’s not easy, but there it is.
create a platformer
I assume you’ve got the time but if you’ve got the money, you can buy a a bunch of assets and decent starter kit from the asset store that makes it possible to solo just about any kind of game you wish to make. If you’ve got the money…
Try whack-a-mole.
You don’t get much simpler than that.
Any idea or passion you have can be made into a “simple” game. The important thing is to focus every aspect of the game on the core idea you want to communicate or express. Big title AAA games are for fun. Indie games are for communication. Don’t just make a game enjoyable, make it mean something and design every aspect of that game around your meaning. This will require some abstract thinking on your part and some imagination of the user’s but the result will be fulfilling and rewarding.
No one can tell you what game you should make unless you have a boss who will pay you to do what he says. I’m guessing that isn’t the case, and seeing as how we aren’t your bosses, do what you want. Not in a juvenile way, in a passionate way. Design a game about what intrigues you and what you want other people to be intrigued by. Share your passion and your ideas with all of us to explore!
If you dont have money to buy art then its got to be something really abstract like geometry wars.
How about tetris then?
Go back in time 10-20 years and look at some simple retro games and do something based on that.
Something like this
http://www.walkerboystudio.com/html/unity_training___free__.html#unity3game3
Only thing is spend some time on obvious modifications such as your own art work, sounds, story etc
If you want something slightly more advanced than Pong, then make a 3D table tennis game with Physics.
This was one of my first Unity projects I did and it was a great learning experience.
You don’t need characters, just a room with a table, net (use some cloth physics :)) and two bats and a ball.
It’s a great little challenge to get the hitting of the ball to work correctly.
Or how about Super Mario from Nintendo64. That was an awesome 3D experience game. But first, you can try and make a 2D version of Mario to understand how AIs, colliders, triggers, menus, modelling and so on work.
Mighty Wings was created in this terms “one man army”
3 months of work.
Cost: 0$.
Some return from 400.000 plays (Wooglie share ads gains)
And a lot of fun working at it.
You have to learn something about everything: Coding, modeling, music, sounds, game design and so on.
Sharp your skills project after project… share results, get feedback.
If you find a team to work with, great, but most of people that says that want to make games lacks stamina, lacks skill (or persistence to learn) and will quit in the long run.
This is especially true when a project is based in pure passion and not money.
There is no such thing as a game costing 0$ to make.
If it took 3 months of work, you need to assign an hourly rate to those hours, and that is the actual cost.
I know they say “Time is Money”, but there’s no need to do a conversion when talking about cost. He already stated ‘3 months work’ which is how much time was spent. That is the cost.