How to come up with a good idea for a game?

Be tough on yourself. When you get those extra ideas write them on a pad or post it note & not in code

 

If there's something that you'd like to play, but isn't available in any game, you can use it as a challenge.

For example, what if you wanted to play an RPG where you could customize your character appearance at will? You could end up with an RPG with a minecraftian element where you forge your armor plaque by plaque.

 

If someone's covered this already, whoops

A big part of being creative is having a good toolbox.

When I was doing painting for gunpla, I'd have ~7 brushes in front of me, half of which I modified for specific brushwork.

When building micro-scale mecha out of Lego, I have a stable of joint designs ready to be reused or modified for the build at hand.

Having a good toolbox that you're comfortable with lets you start slapping things together to see what sticks. Hypothetical example: take that ball rolling code from your toolbox, slap it together with some A*, throw in that dungeon gen algorithm, and see if it's fun. Depending on your toolbox, that was an hour or three of work. You can then scrap it or iterate further.

With a good toolbox, you can iterate quickly, and easily find new ways to use those tools. Without a good toolbox, too much time can be lost in implementation, which can disrupt your creative flow.

Well crap, that was a big ol' ramble -.-

 

If you've seen Game of War and lots of other successful games in the store you know that the actual art assets you have is not the problem.

There are plenty of very serviceable art assets that can be used to make successful games. The problem with the art assets is not the quality of them for the most part but the lack of advertising budget of those that must use such assets.

Truthfully, since I did next to no gaming in the 2000s, when I started getting interested again with the iPhone, I assumed a lot of the game models used in many different games were stock from competing game makers because they have the same aesthetic. Really, they go to the same training schools, using the same 3D software, to be presented on the HW with the same limitations - yeah, getting a hold of very current and acceptable art work for a game is the least of your problems. Even if you think using stock art assets as is from the Unity Asset store is a problem then it's easy to retexture those art assets and truly make them look original such that you'd have to tell the player or they'd need to be looking for it to recognize it was the same asset.

I'd say your bigger problems lies in leveraging your programming skills to do something original and fun with those assets. Good art is no longer the problem.

If you want your own style them maybe it's time you consider yourself a art creator 1st and a game maker 2nd. That's the only way you will prioritize making good original art that you personally like over trying to make money from a game.