Neo Geo compatibility
The Neo Geo home consoles are compatible between regions, you'll find that Japanese consoles have things like red blood and gore whereas the US region console is more of a grey or white colour. Saying that there are mods available such as the Universe BIOS which can change the region of the console and even the type (it can turn a home console into an arcade MVS version or vice-versa).
The Neo Geo home console (the AES) is quite pricey and seems to hold it's value fairly well. Some of the rarer games can go into the thousands on eBay, especially as some games were very limited in release on the AES. However the arcade versions (the MVS) tend to be much more reasonable, although then you have to look at getting a Neo Geo MVS board and something to run it on (it's an arcade board so it'll need some sort of power supply, joystick and a way of connecting to your display... in Europe that's not so much of an issue as most older TVs have Scart inputs which will work, but I gather in the US and Japan you'd possibly need an RGB monitor or something to convert from RGB into component or composite video).
Other option for cheaper games is to get an MVS to AES console converter which allows you to use the arcade MVS carts on the AES console although they can also be pricey (without it the arcade carts won't physically fit in the home console, something I was gutted about when I was a Neo Geo owner back in the late 90s and looking for a cheap supply of games).
It's a great console and well worth the time and investment. Sure it can be emulated on a Raspberry Pi, PC or even a Wii, but there's something about having the actual machine with the massive carts that you just can't get with emulation.
Some links for you... Universe BIOS - http://unibios.free.fr/
Possibly the best Neo Geo resource on the Internet... http://neo-geo.com/
Rob