Hi,

I'm working on a jump'n'run adventure game similar to “Donkey Kong” or “Ori and the Blind Forest” and I wanted to get some feedback on the game art assets. 

You play as a grumpy floppy disk (a.k.a. "Save-Button" in most programs lol) trying to survive the inner mechanisms of a modern computer after being thrown away by his owner as he upgraded to the new format named “CD”.

Well, I would prefer to draw the graphics for the game in a projection that has no depth like e.g. in old school Mario or Sonic for better coordination and timing for jumping, but on the other Hand I really don't like the look of it.

It seems really plain and I miss having an additional dimension to draw details or to elaborate the structure/form.

Here are some example assets:

I would like to hear your opinion about which projection you would prefer. I'm open for opinions about the assets too. Thanks.

A flat 2D game (like Mario or Sonic, as you said) will probably fit the theme just fine. For more interest, you can use multiple planes that scroll at different speeds ("parallax scrolling").

Since you don't have a realistic setup here, I don't think you have to go with realistic graphics for the inside of a computer. Look at what Tron got away with as a representation of the inside of a computer. I'm not saying you can't be more literal than that, but make sure that whatever graphics you use help your gameplay and look interesting.

For me ‘no projection’ clearly wins, even ignoring the advantage for the game.
For power supply, it took me seconds to realize the right part is meant as side view. For the motherboard it took me a whole minute, because it really gets lost in high frequency details. 
What you tried works well for isometric games, but not so much for side scrollers.

But i'm worried about something else: If you use such HF detail the whole game might get lost in that. E.g. The motherboard as background and you won't spot the tiny floppy anymore. It all becomes too fuzzy. But this happens also if you use it as foreground.

Super Mario works quite differently: It has thick rounded borders around tiles like bricks to hint lighting. Larger connected areas like grass / rock have detail only at the boundary, but not inside. Inside it's subtle details and large area of similar color.

Edited the mainboard:

I made the thin 'wires' (don't know the proper name) as green as the rest, so the other parts pop out and become visible. It's still much too fuzzy, but we start to see individual components without having to search for them. So you can use HF detail, but then you have to reduce color variation and contrast to leverage.

I would do the same for the PSU. Imagine the floppy walks on top of it, it would be hard to see. If you turn the cooling grill from silver to black as well, the PSU detail no longer distracts focus and red floppy on top comes into attention.

You can add some “fake depth” by adding cast shadow on the side of the components, like the transistors and other things that would stick out.

It will look more 3d and give you room to create more detail and interest, and still be actually flat.