What are the average system requirements to play the latest games?

It's very subjective. It all depends on what you expect out of your gaming experience and a few other things. I would say that minimum specs for most games are:

Core 2 Duo E8600
4 GB RAM
nVidia GT240

This would let you play most current games on at least medium settings at 1080p resolution with playable (25+ FPS) framerates. This machine is by no means capable of running games on all high at 1080p, you will have to sacrifice screen resolution in order to accomplish this. Also, forget about AA/AF with this setup.

It depends on what game you are considering, resolution and a lot of other factors.
But the minimum by today's standards means having at least a modern dual core CPU and 2 GB RAM( less RAM might cause problems in some games).The minimum requirement for the Graphics card depends on the resolution but the least I'd go for is a HD 4650/ 4670/5570/ 5550 GDDR5 and similar cards.

Do you want to learn technical skills? It sounds a lot like you have interests beyond just playing the few most popular games of the time. Just get a PC!

PC hardware is already obsolete when you take it out of the store, architectures are supposed to last only as long as it takes to push a better generation to the market. But systems do have a lifespan and depending on the level of the original spec and the age of the system they can do different things. I'm used to my main gaming systems lasting maybe 2 years in the intended use after purchase - but the cycle is probably getting longer nowadays, as games don't have to push the graphics/hardware envelope that much to be new and interesting. Later in the lifecycle there's things like retro gaming - just recently I was running some PC games that were released in 1992 and 1996, and they were rather enjoyable. Sure graphics do age but good game design lasts longer! Also, you can just install Linux on the old puter and use that to learn A LOT about computers.

You can get a good idea of what is considered a low-end or a mid-end gaming system by taking a look at one of the buyer's guides for one. Anandtech, Tom's and other tech sites put those out at a rather regular basis. If you have a guide that's fairly new and has a system that sounds nice, you can just go out and buy the same parts (or something very similar). These forums have very nice sticky threads that contain a lot of well-organized information for homebuilders. And asking questions on the forums is often a very good way to get forward. Of course it can help even more if you know someone you can discuss it through and who can help you build the system.

You can get a very nice build for $1000.
There is no need to spend more.

look at videos for minecraft - perfect example of gameplay more important than pretty graphics.
I have seen building tools/weapons in early Resident Evil and RPGs.
I would love to see something that blows me away like in the Ole Days.
I remember when Zaxxon 3d, Dragons Lair Laserdisc game, Duke Nuke Em came out and were awesome (maybe it was just youth?)
I read about Kinect being used by creating an avatar and interacting online with other users (too bad M$ wont allow porn usage of Kinect LOL)
Also referring to Fable and decisions in game affecting character developement need to be explored.
How about a game where the littlest decision you make will affect your character and gameplay.
With primitive forms of A.I. being used in games combined with decision-changing gameplay plus Kinect and 3D there has to be more than fragging zombies/cyborgs/aliens.
Just something off ot the top of my head would be a real life based game in modern setting where you start off as young guy dealing with gangs and the decisions can affect how other AI characters treat you,how you look etc and you can
end up being a gang leader or police officer or bum etc while using the Kinect for battle and body language.
No aliens just real life scenarios in real life settings
Call it "Reality Gaming"

haha, I have a 2001 Toshiba laptop, it's so fun screw it up reintall random OSs, I tried Ubuntu, Xubuntu, Lubuntu, Puppy and run starcraft 1 at max settings on it's ATI radeon mobility M6.

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Got it? =)