I agree. $800-1000 is a more realistic budget for a 3-4 year gaming PC without too many compromises.

It's a solid i5-4690K/ GTX 970 based build. 

Those two compents run about $230 for the CPU and about $330 for the video card alone. 

Spent some more money to build a pc with an intel i5 cpu , a r9 280x or a simillar vga , a good brand psu around 700 kwatt , cheap 8-16 gb ram , and cheap hard disk and case.
That way , after some years that you will have problem with games you will need to replace only the gpu.

Seconding this.

50-60% of the overall cost should go into your GPU and CPU alone, then a midrange PSU minimum, don't cheap out on the PSU because the nasty cheapo units will cost you dearly when they die and take out half of your system with them.

CPU and GPU make the biggest impact on the resulting pc's performance, memory makes very little difference beyond capacity, motherboard? just go with one that is compatible with the cpu and gpu, and has the features you NEED.

If theres enough cash left i'd recommend a decent modern SSD for OS/Applications and a 1tb+ mechanical hdd for file storage, aim for 120gb or higher for OS drive, beyond gpu and cpu an SSD makes a big difference to the overall experience.

Don't fall in to the trap of spending hundreds on a fancy case, its money that would be better spent on power, no use a computer looking good if whats inside it sucks.

I worry about compatibility like you do to but what you want to start looking at first is the case, motherboard, and power supply ... 

Forget about the CPU or the GPU, just focus on picking out these three parts first ...

For the case, I recommend an "ATX Mid Tower" sized case since it is compatible with large video cards and that's ideal for getting more performance. (Get this part new.)

As for the motherboard, get one that's compatible with an LGA 1150 CPU socket AND it MUST also have a PCI Express 3.0 expansion slot. (Get this part new and just one expansion slot is enough.)

You also want to get a 600+ watt power supply with at least 2 6+2 pin PCIE connectors. (Get this part new.)

I have another question, what will be your display ?

At your pricetag, it's really difficult to make a rig that can play in full HD over several years.

Best would be to invest most into a graphics card, since this one is the most limiting part at your budget. A Radeon 270/270X/280 would be your best bet (NVidia is too expensive for you, even a GeForce 960 is more expensive than those mentioned). The 270 can be found for 150€/$, the 270X for about 180 and the 280 costs around 200$/€.

Since the graphics card is the limiting factor, you won't need a high-end CPU. An i5 4440 (around 170€/$) would amply suffice. You could even go and buy an AMD CPU like the A8 7600 (around 80$/€) or an A10 7850 (around 120€/$) without losing much performance at that point.

Next, you'll need some Memory. 8 GiB of Ram (prefer 2x4 GiB instead of 1x8 bith for price and performance) will cost you about 50$/€

A Motherboard can be found for 50$/€, but these are very bare-boned; I suggest looking more somewhere around an 80$/€ pricetag. Boards for Intel CPUs are sensibly more expensive than AMD boards (most Intel boards cost over 100$/€, most AMD boards less than 100)

What you need now are a casing, a power supply unit, a hard drive and a DVD drive for your rig to be completed, which will cost around 150$/€ if you take cheaper components.

The main Rig would be completed with this, for a pricetag of 500-600$ as you asked.

The problem is: You are still missing some vital parts. You'll need a Windows licence for most games (dunno the price in the US, but I guess around 100$), Keyboard, Mouse and possibly a Gamepad (cheap Keyboard/Mouse combos can be found for 10-20$, the gamepad however will cost about the same as on a console), and a monitor unless you want to connect your rig to your TV screen (100$ minimum, 150 if you want some quality)

Long story short, at that price it's hardly feasable to make a decent gaming rig. I would follow Tachikoma's suggestion and wait until you can spend at least 800$ to build your rig

One last note on pre-build PCs: These use generally either very low grade hardware (especially for the mainboard, RAM and the PSU) or are overpriced (often both), and most of the time they are very unbalanced, too, so I wouldn't go that route if you can avoid it.

Building a PC that will play games on high/max settings for 10 years just doesn't happen.

No 2005 components would play the Witcher 3 on max settings.
Best you can do is build a good 500 dollar PC and if you're not gonna upgrade, deal with gradually lowering settings over the years.

I would save up to at least to 900$, because then you will be able to get 1080p with 50-60fps on almost all games, everything under 700-500$ will be outdated quite fast. Cause even at a budget at 500$ i would recommend buying a solid motherboard for later upgrades.

this should help you get a ton of idea - https://pcpartpicker.com/

I feel like posting a bunch of newegg links to products but I will refrain. However, I will recommend you get an i7 CPU and a good Nvidia GPU

probably worth going for i5 though, dual core just won't always cut it